Causal dimensions of college students' perceptions of physical symptoms

According to attribution theory, controllability, locus, and stability are important dimensions underlying causal explanations. The extent to which these theoretical dimensions underlie lay explanations for physical symptoms is unclear. Accordingly, in this study, attributes relevant to the lay public were empirically derived using a multidimensional scaling (MDS) procedure. Undergraduates (N=194) provided similarity judgments for 18 potential causes of physical discomfort. The MDS analysis yielded a three-dimensional solution. The first dimension captured the distinction between physical and nonphysical causes. The second dimension distinguished either variable versus stable causes or those that are controllable versus uncontrollable by health care professionals. The third dimension differentiated causes under low versus high personal control. These findings empirically confirm the theoretically proposed dimensions of personal control and stability and suggest the utility of considering the physical/nonphysical and controllability by health care professional distinctions in future work on attributions in the health domain.     

Convergent inputs from articular,cutaneous and muscle receptors onto ascending tract cells in the cat spinal cord

Summary 1.Responses were recorded from 160 ascending tract cells in segments L4 to L6 of the spinal cord in chloralose anaesthetized, spinalized cats. The tract cells were identified by antidromic activation following stimulation of pathways in the lateral and ventral funiculi at the level of the spinal cord transection at the thoracolumbar junction. Axonal conduction velocities ranged from 9 to 114 m/s. 2. A sample of 152 of the neurones examined could be subdivided according to the distribution of their receptive fields into 49 cells activated just from receptors located in skin (s cells), 17 neurones excited by receptors in deep tissues (d cells), 15 units with a convergent input from receptors in skin and deep tissues (sd cells), and 25 neurones with a convergent input from the knee joint and either skin (sj cells), deep tissues (dj cells) or both (sdj cells). No receptive fields could be demonstrated for the remaining 46 neurones. 3. S and sj cells were found almost exclusively in the dorsal horn, whereas many d, sd, sdj and dj units were in the ventral horn. Almost all of the cells that lacked receptive fields were in the ventral horn or intermediate grey. 4. Ninety-one of 158 cells (56%) demonstrated no background activity. Of these, 43 cells (27%) lacked receptive fields. Many of the silent neurones were in the ventral horn, but some were in the dorsal horn. Of 25 cells having knee joint input, 18 (72%) had background activity. 5. All of the neurones that had a receptive field in the knee joint also had a convergent input from receptors in other tissues. In 3 cases, there was a receptive field in the skin over the foot (sj cells). For 16 cells, receptive fields included not only the knee joint but also skin and deep tissue (sdj cells). Usually, the cutaneous receptive field was near the knee joint, but sometimes it was remote, such as on the foot. The deep receptive fields were chiefly in the muscles of the thigh and/or leg. For 6 dj cells, the receptive fields included not only the knee joint but also deep fields like those of sdj cells. 6. Cutaneous receptive fields were classified as low threshold (cells excited best by innocuous intensities of mechanical stimulation), wide dynamic range (cells activated by weak mechanical stimuli, but the best responses were to noxious stimuli) or high threshold (innocuous stimuli had little effect, but noxious mechanical stimuli produced a vigorous discharge). Similarly, stimulation of the knee joint with weak mechanical stimuli could excite some neurones, while others could be activated by weak or strong articular stimuli but were excited best by noxious stimuli, and still other neurones were activated by knee joint stimuli only if the intensity was noxious. 7. In several instances, contralateral receptive fields were noted. These were generally in deep tissue or in the knee joint. 8. It was concluded that many of the responses to articular stimulation of the spinal cord ascending tract cells examined in this study could have been mediated by the fine afferent fibres that supply the knee joint. Although further work will be required to determine which particular ascending tracts transmit nociceptive information concerning the knee joint, it can be proposed that many of the responses demonstrated here were likely to play a role in either joint pain of in triggering responses associated with joint pain.     

Foraging strategies ofDrosophila melanogaster: A chromosomal analysis

Two larval foraging strategies inDrosophila melanogaster were identified, rover and sitter. Rovers traverse a large area while feeding whereas sitters cover a small area. The difference between rovers and sitters was analyzed genetically by chromosomal substitutions between isogenic stocks. Differences in larval locomotor behavior (crawling behavior) can be attributed to the second chromosome, the rover strategy being dominant over the sitter strategy. Differences in feeding rate (shoveling behavior) are affected additively by both the second and third chromosomes. Natural populations ofDrosophila larvae were sampled three times over a 2-month period; rovers and sitters were at constant frequencies in these populations. The two foraging strategies are discussed in the light of resource utilization in environments where food is distributed continuously or discontinuously.     

An hypothesis regarding the cortical mechanisms of operative memory

Investigations of the neuronal activity of the cerebral cortex of monkeys during the performance of a delayed spatial choice made it possible to formulate an hypothesis regarding the neuronal systems providing for operative memory. One system functions on the principle of relay race-reverberation transmission of information. During the action of a sensory signal a population of spatially selective sensory neurons is excited. By the delay period (operative memory) this information is transmitted to a population of memory neurons. The delay period is quantized in time segments in the course of which individual populations of cells are involved in relays in the reverberation activity. Each of these populations comprises a neuronal trap in which the excitation circulates for 1.5–2 sec. At the end of the delay period switching of the excitation to a different population of cells takes place, which are associated with the preparation of a goal-directed movement (the neurons of the motor programs). Another system of neurons assures the reliability of the transitional phases of the above-named processes, specifically: 1) of the switchings of information from the sensory neurons to the memory neurons and subsequently to the neurons of the motor programs; 2) the reflection of the entire period of operative memory without relay race-reverberation; and 3) the preservation of the signal information in the activity of a unified neuronal population right up to the moment of the performance of the goal-directed movement. The above-designated systems are represented variously in the associative (frontal and parietal) zones of the neocortex.Translated from Zhurnal Vysshei Nervnoi Deyatel'nosti imeni I. P. Pavlova, Vol. 41, No. 6, pp. 1088–1093, November–December, 1991.     

On the existence of a lyotropic and osmotic type of collagen swelling produced by representative electrolytes and anelectrolytes

Summary The influence of NaI, NaCl, urea, glucose and sucrose on venous tissue volume were studied with regard to osmotic (electrostatic and dehydrating) and lyotropic effects. NaI leads to the highest volume increase and to the extreme irreversibility of this change. The tested anelectrolytes cause a decrease of tissue volume over the whole range of concentration with the exception that, beyond 1.0 osM, urea causes an increase. The large reversibility of this increase is pointed out. A strict discrimination between osmotic and lyotropic volume change is questioned.     

A cyclin protein modulates mitosis in the budding yeast Saccharomyces cerevisiae

Summary For the budding yeast Saccharomyces cerevisiae the mitotic cell cycle is coordinated with cell mass at the regulatory step start. The threshold amount of cell mass (reflected as a critical size) necessary for start is proportional to nutrient quality. This relationship leads to a transient accumulation of cells at start, termed nutrient modulation, upon enrichment of nutrient conditions. Nutrient enrichment abruptly increases the critical size needed for start, causing the smaller cells, produced in the previous cell cycle, to be delayed at start while growing larger. Here we show that, in S. cerevisiae, a second cell-cycle step, at mitosis, also exhibits nutrient modulation, and is, therefore, another point of cell-cycle regulation. At both mitosis and start, nutrient modulation was found through mutation to be regulated by the activity of the cyclin-related WHI1 (CLN3) gene product.     

Intratypic antigenic heterogeneity of Coxsackie B viruses

Summary Neutralization tests, employing the cytopathogenic effect in tissue culture tubes, with a variety of homotypic antisera and strains of Coxsackie B viruses often yielded high titers in early readings and low titers in late readings — the break-through phenomenon — and occasionally also low, early-reading titers with heterologous, homotypic sera, which gave high titers with the homologous strains. Of 27 strains of Goxsackie B 1 to B 5, that were tested, 10 showed no break-through tendency while others showed varying degrees of break-through, without reference to any evidence of intratypic antigenic variation. There was a positive correlation between a small number of tissue culture passages away from man or mouse brain and the break-through tendency. Moreover, strains without break-through tendency yielded viral populations with marked break-through properties after a single intracerebral passage in newborn mice, and even after two subsequent tissue culture passages. Plaque-purified progeny exhibited the break-through phenomenon to the same extent as the original, unpurified cultures.The early readings yielded reproducible titers, which could be used for analysis of antigenic variation. Prime antigenic variants, of broader antigenic constitution than their non-prime relatives, were found among the Coxsackie B 2, B 3, and B 4 strains that were tested. These prime strains (e. g., B. V. A. 96- B2; Stevens - B 3, and Burrier or J. V. B. - B 4) were found to be antigenically broader than the prototype strains (Ohio 1 - B 2, Nancy - B 3, Powers or Texas 13 - B 4) generally used for the preparation of diagnostic antisera. The broader antigenicity of the prime variant was also present in plaque-purified progeny.Aided by grants from The National Foundation, Inc.The work reported here was carried out in 1957–1958 during Dr.Wigand's tenure of a fellowship in the Cincinnati Laboratory.     

Application of the polymerase chain reaction to study the M protein(-like) gene family in beta-hemolytic streptococci

Evaluation of homologous regions of published M protein (emm) gene sequences from group A streptococci (GAS; Streptococcus pyogenes) was used to design three primer pairs for polymerase chain reaction (PCR) and three oligonucleotide probe sequences internal to the amplified products. One set of primers and corresponding probe should detect and lead to amplification of emm(-like) genes of virtually every type (all M), another (SOR^-M) should only amplify emm(-like) genes from GAS negative for serum opacity reaction (SOR) and the third (SOR⁺M) should expand only emm(-like) genes from SOR⁺ GAS. Using the all M primer pair for PCR on the genomic DNA from GAS of 29 different M types as well as from a group C and a group G streptococcal isolate, DNA fragments within the expected size range were amplified in every assay. All PCR products reacted with the all M probe. Related sequences were not detected in genomic DNA of an S. agalactiae and an Enterococcus faecalis isolate. Applying the SOR^-M and SOR⁺M primers to identical assays led to mutually exclusive amplification products. The SOR⁺M and SOR⁺M probes hybridized only to their corresponding products. Exceptions to this exclusivity were the SOR⁺ GAS of M types 3, 8, 27, 34, 42, 67, and 69, which consistently reacted only with the SOR⁺M primer/probe set. Analysis of sequence data from the amplified emm(-like) 2, 3, 18, and 19 genes revealed interesting specific features such as conserved gaps in the C-terminal sequence regions from SOR⁺ and the exceptional SOR^- GAS strains. These data indicate the existence of a subgroup of strains among SOR^- GAS and may advance our understanding of phylogenetic relationship between different serotypes of GAS.     

Effect of the degree of myocardial hypertrophy associated with an experimental heart defect on the resistance to altitude hypoxia

Summary Experimental coarctation of the abdominal aorta with constriction of its lumen to one-third of the original diameter was created in 18 albino rats. Four months later various degrees of myocardial hypertrophy developed in the animals with a relative weight of the heart ranging from 0.0033 to 0.0069. In elevation in the barochamber, the altitude ceiling of the animals with a relative cardiac weight below 0.0040, did not differ from the normal one. The altitude ceiling proved to be considerably decreased in animals with a relative cardiac weight of over 0.0040. Analysis of ECG recorded during the elevation demonstrated that in the animals with a considerable myocardial hypertrophy reduced resistance to the acute high altitude hypoxia depended on the reduction of the functional resistance of the heart.(Presented by Active Member AMN SSSR V. V. Parin) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 55, No. 5, pp. 37–40, May, 1963     

Oncogenic activity of the BK type of human papova virus in inbred rat strains

Summary The oncogenicity of the human polyomavirus BK (BKV) was tested in newborn inbred rats.It was found that the tumor rate was negatively correlated with the levels of T antibody 3 months after inoculation and the frequency of animals with detectable T antibodies 1.5 months after inoculation.By contrast, no influence of viral HI titers on the tumor rates was found. Thymectomy of animals resulted in most experiments in increased tumor rates. Inoculation with BKV of animals later than 24 hours after birth yielded a decrease of tumor rates.The results obtained suggest that T antibody titers present at a critical time after inoculation are associated with low oncogenicity of BKV.The oncogenicity of BKV was comparatively tested in rat strains possessing the allele l or the allele a, respectively. The oncogenicity was significantly higher in rats with the allele l than in rats with the allele a. Rats with the allele l showed lower T antibody response than rats with the allele a.These differences could be explained by the finding that cells of a origin showedin vitro a higher percentage of T antigen bearing cells than did cells of a strain possessing the allele l. In comparison to previous results obtained with BKV inoculated outbred WISTAR rats, the oncogenicity of comparable BKV doses in inbred rats was generally higher and the latency period of tumor manifestation shortened.     

Biophysical studies of teschen disease virus (Talfan strain)

Summary Studies have been made of the heterogeneity of infectivity and CFA in Teschen virus (Talfan strain) suspensions. Most of the infectivity was contained in two components of densities 1.46 gm./ml. and 1.35 gm./ml. The physical, chemical and immunological properties of these components have been compared. It was possible, however, to convert a large proportion of 1.46 component to 1.35 component by treating the 1.46 component with sodium dodecyl sulphate. This would indicate that the 1.46 component was a complex formed between the infective particles and cellular debris.Further studies on the growth characteristics and electron microscopy of the virus have been made.     

Coronary blood flow in rats native to simulated high altitude and in rats exposed to it later in life

Summary In rats exposed to a simulated high altitude of 3500 m for their whole prenatal and postnatal life a severe cardiac hypertrophy develops. In rats born and first staying 5 weeks at sea level and then being exposed to simulated high altitude, only a unilateral right cardiac hypertrophy occurs. In both groups nutritional coronary blood flow was estimated in left ventricle, right ventricle, and septum and was compared with control animals of similar age. Coronary blood flow was measured at hypoxia in all groups. At first cardiac output was determined by the Fick principle, then⁸⁶Rb was applied and the animals were killed after 55 sec. Activity of⁸⁶Rb was measured in both cardiac ventricles and septum and the fractional uptake was calculated. According to Sapirstein (1956, 1958) the distribution of⁸⁶Rb follows the distribution of cardiac output and from both these data the nutritional blood flow to the parts of the heart may be estimated.Cardiac output was similar in rats exposed to simulated high altitude later in life (newcomers) and in control animals, but it was significantly lower in rats born in the low pressure chamber (natives).Fractions of cardiac output supplying cardiac ventricles and septum in rats from both hypoxic groups were significantly higher than in control animals. In the natives they were significantly higher than in the newcomers. The fractions of cardiac output in both newcomers and natives remained significantly higher than those of the control animals, also when calculated per gram of heart tissue.Nutritional coronary blood flow (in ml/min) was higher in both ventricles and septum of the newcomers and in the right ventricle of the natives, and lower in the septum of the natives, when compared with control animals. Coronary blood flow per gram of heart tissue (in ml/min·g) was significantly higher in all cardiac parts of the newcomers, but it was about the same in all cardiac parts of the natives when compared with controls.The importance of observed changes concerning myocardial tissue oxygenation is analyzed by using Krogh's cylindrical tissue model.Presented in part at the XXVIth International Congress of Physiological Sciences, New Delhi, India, October 20–26, 1974.     

”Reflexes of purpose and freedom” in the comparative physiology of higher nervous activity

The most complex unconditioned reflexes of aim and freedom, discovered by I. P. Pavlov, are compared with the competence drive and the motivation of the resistance to coercion, respectively, described by contemporary ethologists. On the basis of the unconditioned reflex of purpose, conditioned reflexes were developed in which positive emotions arising in connection with the perfection of a skill, irrespective of its pragmatic significance at a given moment, serve as the reinforcement. The unconditioned reflex of freedom is regarded as a phylogenetic precursor of the will, and its acute extinction as the physiological mechanism of hypnosis. It was demonstrated experimentally that the appearance of the state of animal hypnosis (immobilization catatonia) in rabbits is accompanied by the predominance of electrical activity and heat production in the right hemisphere, i. e., by symptoms which are found in hypnosis in man.Translated from Zhurnal Vysshei Nervnoi Deyatel'nosti imeni I. P. Pavlova, Vol. 39, No. 3, pp. 415–420, May–June, 1989.     

Präzisierung der Reizwirkung mittelfrequenter Wechselströme

Zusammenfassung Bei der Mittelfrequenz-Impuls-Reizung ist streng darauf zu achten, daß keine polaritären Reizkomponenten auftreten. Die diesbezügliche Kontrolle wird am besten mit Hilfe des Konvertibilitätstestes vorgenommen, d. h., es darf beim Vertauschen der Zuführungen zu den Reizelektroden weder die Reizschwelle bzw. die Größe des kollektiven Reizerfolges noch dessen Latenzzeit eine signifikante Änderung erfahren. Auf diese Weise wird die Phasenunabhängigkeit des echten Mittelfrequenz-Reizeffektes nachgewiesen.Diesen Anforderungen entsprechen Mittelfrequenz-Impulse, deren Trägerfrequenz über einige wenige Perioden sich aufschaukelt und ebenso wieder abklingt. Demgegenüber sind Mittelfrequenz-Stromstöße mit phasenstarrem Einsatz und Ende nicht unbedingt frei von polaritären Ein- bzw. Ausschalt-effekten, indem sowohl die erste als auch die letzte Trägerperiode einen polaritären Wechselimpuls-Reizeffekt ergeben kann, je nach Phasenlage bezogen auf die wirksame Reizelektrode und Art der Ansprechbarkeit des Reizobjektes (Nerv) auf entsprechend kurze gleitspiegelsymmetrische Wechselimpulse. Für eine echte Mittelfrequenz-Stromstoß-Reizung ist demnach ebenfalls ein Aufschaukeln und Abklingen der Trägerfrequenz über einige wenige Perioden erforderlich.Es besteht ein prinzipieller Unterschied zwischen der echten Mittelfrequenz-Reizung, die phasen -bzw. periodenunabhängig ist und schon früher als apolaritär bezeichnet wurde, und der konventionellen polaritären Reizung, die als polaritäre Komplikation der Mittelfrequenz-Reizung auftreten kann.Diese Präzisierung der Reizwirkung mittelfrequenter Wechselströme wurde angeregt durch zwei im Text erwähnte Publikationen, in denen in keineswegs überzeugender Weise versucht wird, die Mittelfrequenz-Reizung letzten Endes auf das polare Gesetz der Erregung zurückzuführen.

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Summary The particular excitatory action exerted by middle-frequency alternating current can only be revealed if care is taken to eliminate the occurrence of so-called polarity effects. Such effects are produced by the short alternating impulses represented by the first and the last period of a middle-frequency current pulse and are based on the polar law of excitation.In order to prevent such polarity intrusions, it is necessary to increase and decrease the amplitude of the middle-frequency current pulses over a few carrierperiods, or, to use amplitude-modulated middle-frequency impulses of variable shape and duration of envelope.A true middle-frequency excitatory effect is easily demonstrated by resorting to the convertibility test. It will then become evident that stimulation threshold, magnitude as well as latency of response do not change during reversal of the stimulating poles. This means, that no significant phase change of the response with regard to the carrier-frequency occurs when the leads to the stimulating electrodes are commuted, and that, as a result, true middle-frequency effects do not depend upon one particular catelectrotonic variation among the carrier-periods of a middle-frequency current pulse.It can thus be concluded that a fundamental difference exists between true middle-frequency stimulation, which is based on a non-polarity or apolarity principle, and the conventional stimulation of the polar or polarity type.This paper has been written in the hope of dispelling some errors of interpretation (discussed in the text) tending to ascribe the excitatory effects of middle-frequency impulse stimulation to the classical polar law of excitation.

     

Lability in the responses of cells in the auditory cortex of squirrel monkeys to species-specific vocalizations

Summary The activity of 28 cells located mainly in the secondary auditory cortex (A II) of awake squirrel-monkeys, was extracellularly recorded for periods of up to 6 h. Seven different species-specific vocalizations, which were repeatedly presented to the monkey, were used as auditory stimuli. Twenty-six cells responded, at least once, to one or more vocalizations; 22 cells revealed some change in their response (pattern or strength) to at least one vocalization (change in response). Twenty-one cells exhibited a change in the number and/or type of vocalization to which they responded during the recording period (change in selectivity). At some time during the recording period all the responding cells exhibited a change in response and/or a change in selectivity (change in responsiveness). A change in response of a cell to a vocalization did not necessarily exclude a change in selectivity, associated with the same vocalization, later in time and vice-versa. A change in responsiveness to one vocalization was not necessarily correlated with changes in responsiveness to other vocalizations.     

Destabilization of herpes simplex virus type 1 virions by local anesthetics,alkaline pH,and calcium depletion

Summary The infectivity of herpes simplex virus type 1 (HSV-1) was found to be markedly reduced by treating virions with the tertiary amine local anesthetics lidocaine, dibucaine and tetracaine. These treatments induced a characteristic shift in the buoyant density of the HSV-1 particles from a light to a heavy population. HSV-1 virions were unstable at alkaline pH, and alkali treatment caused the same shift in buoyant density. Ca²⁺ stabilized the light population. These results suggest that the physicochemical status of the HSV-1 envelope which is sensitive to the treatments described above plays an important role for the integrity of the virion.     

Comparison of the estrous cycles in mice of high and low cancer lines

Summary In February and May the author studied the duration of the estrous cycle stages in female mice of high A and low C₅₇ cancer lines. It was established that the average duration of the estrus is much greater and of diestrus much shorter in the A than that of the corresponding stages in the C₅₇ line.The estrous cycles of the C₅₇ line females do not undergo any significant seasonal changes while in the A line they approach the character of the normal mice spring cycles.Desviations from the normal duration of the estrous cycle stages in the high cancer line mice denote a disturbed hypophyseal — ovarian hormonal balance.Presented by Active Member AMN SSSR V. N. Chernigovskii     

Effects of Age and Experience on Mating Activity in the Sibling Species Drosophila pavani and Drosophila gaucha

The effects of age and experience on sexual activity and on intra- and interspecific discrimination were studied in two sibling species of the mesophragmatica group, Drosophila pavani and Drosophila gaucha. Sexual activity of a total of 2970 individual couples of the same or of both species was observed at two ages: 10 days, (young inexperienced) and 18-20 days (old, either inexperienced or experienced, if either the male or the female had copulated previously). In the 1186 (39.97%) pairs that mated, the latency to copula and duration of copula were registered. Age has a different effect in both species: young Drosophila pavani and old Drosophila gaucha females are less receptive to males of either species of the corresponding age. The receptivity of females is also reflected in heterospecific matings, as Drosophila gaucha males increase their mating activity with age. In both species, female receptivity decreases with experience, whereas mating activity of males increases with experience, especially that of Drosophila gaucha toward heterospecific females. Drosophila pavani females take longer to mate than those of Drosophila gaucha. In both species old males tend to mate faster, whereas experience increases the latency to mating in females and decreases it in males. Both species differ significantly in the duration of copula. It is longer in Drosophila pavani than in Drosophila gaucha and is determined mainly by the male. The duration of copula increases with age, especially in Drosophila pavani females, whereas it is reduced in males of the same species.     

Evaluation of mouse monoclonal antibodies raised against an isolate of the variant avian paramyxovirus type 1 responsible for the current panzootic in pigeons

Summary Nine monoclonal antibodies raised against pigeon variant avian paramyxovirus type 1 isolate pigeon/England/617/83 were tested for their ability to react with classical and other pigeon variant isolates. Two of the monoclonal antibodies appeared to be specific for 617/83 reacting with no other virus. The remaining seven monoclonal antibodies bound to cells infected with all other pigeon isolates in indirect immunoperoxidase (IIP) tests but four distinct groups of other PMV-1 viruses were formed on the basis of the binding patterns. One of the monoclonal antibodies 161/617 caused haemagglutination inhibition (HI) of all the pigeon isolates tested but none of the other PMV-1 viruses and these results reflected the IIP results with this monoclonal antibody.161/617 was also shown to inhibit viruses of the avian paramyxovirus type 3 serogroup in HI tests. This reaction and the ability to bind to infected cells in IIP tests appeared to be restricted to PMV-3 viruses isolated from exotic birds and did not occur with viruses of ostensively the same serotype from turkeys.     

The ultrastructure of the “excretory” system of ascaris suum larvae

Summary Electron microscope observations of the excretory cell of the infective larva reveal that it contains a large nucleus surrounded by cytoplasm containing numerous organelles, multi-granular bodies, vesicles and granules typical of glandular cells. The proximal region of the excretory duct bears a number of scattered microvilli, on its adluminal surface, and the distal region is lined with a thin multilayered cuticle.In the liver stage larva 2 days after infection, 2 lateral excretory columns are present. These arise from the excretory cell body and extend posteriorly for about half the length of the intestine. Each column contains a narrow longitudinal canal surrounded by cytoplasm rich in mitochondria, granular endoplasmic reticulum, free ribosomes and large vacuoles. Evidence was obtained of the passage of substances through the wall of the canal but their chemical nature was not determined.Further extension of the lateral columns is seen in the 8-day, lung-stage larva, the columns now extending for more than two-thirds the length of the intestine. Their diameter is also increased but their internal structure is essentially similar to that of the 2-day liver-stage larva.The excretory duct which arises immediately anterior to the nucleus has a structure similar to that of the lateral columns for the first half of its length, the microvilli described in the infective larva being absent at this stage. The distal half of the duct is lined with cuticle.