causing the localization of iKMuatodos in ccitain portions of the 

 (ligestivo tract. 



The possibility that bile salts may affect the growth of in- 

 testinal parasites has been recognized for some time. Accord- 

 ing to Moorthy (l!t3.")) fresh bile from certain si)ecies of Barbiis 

 and from sheep and man is capable of killing Ci/clops and of 

 activating the enclosed larvae of linu-iinciihis mrilini iisix to es- 

 cape. De Waele (liHU) claimed that the eestode, Taenia kyda- 

 tigena {Cysticcrcun pixiformis), is able to infest dogs because 

 of the absence of Na-glycocholate in dog bile and that since 

 Na glycocholate is toxic to the organism it can not develo]i in 

 animals which secrete this substance. 



Davoy (1938) has investigated the effect of bile salts ou 

 sheep nematodes. He found that the species which infest the 

 duodenum (Trichostrongylii.s colubriformis and T. vilriiius) of 

 sheep were much more resistant to Na-tauroeholate and Na-gly- 

 cocholate than other species {Ncmatodirim fillicoUis, A', spathi- 

 ger, Coopcria oncaphora, Coupcria curticci, and Ostcrtngia cir- 

 cumcxncta) from the lower small intestine and abomasum. 

 Cooperia curticci, which lives closer to the opening of the bile 

 duct than the other species except Tricliostrongj/lus colubrifor- 

 mis and T. vitrinus, has a resistance second only to Tricho- 

 Ktrongylus. Since the bile salts are introduced by the bile duct 

 and are largely reabsorbed in the snuill intestine, the concen- 

 tration of bile salts decreases along the intestine. The high 

 concentration in the upper small intestine probably prevents 

 species other than Tricliostrongylus from living in that region. 

 In these experiments glj'cocholate seemed to be somewhat more 

 toxic to Trichostrongylus than tauroeholate. Davey mentioned 

 the possibility that difi'erential susceptibility to the two bile 

 salts might be a factor in the determination of host specificity. 



The products of bacterial decomposition are of several types: 



1. Products of carbohydrate decomposition from: 



a. Hydrolysis of cellulose to glucose in the rumen and 

 large intestine of herbivores. 



b. Fermentation of simple sugars to lower fatty acids in 

 the small and large intestine of all vertebrates and in 

 the rumen of ruminants. 



2. Products of protein decomposition from: 



a. Hydrolysis of proteins to amino acids in the upper 

 small intestine. 



b. Fermentation of amino acids to aporrhegmas and to 

 lower products in the lower small intestine and large 

 intestine of animals with simple stomachs and in the 

 rumeu of ruminants. Some of the products of fermen- 

 tation are indol, skatol, paraeresol, phenol, volatile fatty 

 acids, H=S, histamine, and tyramine. The relative 

 amounts of these products depend on the type of pro- 

 tein and on the species of bacteria present. 



At present there is little evidence that these substances are 

 useful or harmful to intestinal nemas. Glucose is probably 

 absorbed by nemas, and on this assumi)tion changes in the diet 

 or in the bacterial flora which would affect the distribution of 

 glucose should affect the parasites. From the studies of Grove, 

 Olmstead, and Koenig (1929) on the low'er fatty acids in feces 

 it seems as if the quantity and perhaps the distribution of these 

 materials along the digestive tract is greatly affected by diet. 

 It is also probable that the products of protein putrefaction 

 may exert beneficial or harmful effects on the parasites. If 

 so, then experiments in which the amount of protein putrefac- 

 tion is controlled are in order. Such control is possible by the 

 administration of large amounts of lactose and bacteria which 

 ferment glucose to acid (review, Arnold, 1933). This treatment 

 results in the replacement of the protein putrefying organisms 

 of the coli-aerogenes group by those which ferment carbohy- 

 drate. The change in type of fermentation products is prob- 

 ably due to both the protein sparing action of carbohydrate and 

 the change in flora produced by increased acidity of the intes- 

 tine. Putrefaction could also be decreased by increasing the 

 rate of passage of ingesta. It is possible to increase protein 

 putrefaction at least in the large intestine by feeding such large 

 quantities of protein that some of it escapes complete digestion 

 and absorption in the small intestine. The putrefying organ- 

 isms also increase under conditions of achlorhydria which re- 

 sult in an alkalinization of the intestine, and if the achlorhydria 

 is severe they may even become implanted in the stomach. It 

 seems probable that experimental modification of the intestinal 

 contents through modification of the intestinal flora may bring 

 about changes in the distribution of nemas along the intestine, 

 and perhaps such experiments may result in methods of con- 

 trolling or eliminating certain species. Any changes which 

 may prevent eedysis of larval nematodes might be extremely 

 useful (Lapage, 193S). 



It is known that HiS is highly toxic to vertebrates and that 

 it easily passes through most animal membranes. The studies 

 of Enigk (1936) on the lethal effects of H.S on the eggs of 

 Ascaris himbricoides and the studies of Lapage (193.5) on the 



infective larvae of Triclionlroiigylus suggest that the outer cov- 

 ering of eggs and larvae may be permeable to H2S and other 

 sulfur compounds. Lapage (193.5b) obtained considerable evi- 

 dence that the permeability of the sheaths of larvae is changed 

 by sulfur compounds. In these experiments the effect of pH 

 was not carefully controlled, but the effect of 1 percent Na2S 

 on the eedysis of infective larvae was more pronounced than 

 that of 1 or 2 per cent NaOH. The sheaths became greatly 

 distended due to intake of water. If this effect is really due 

 to the sulfur compounds, this type of effect may give a chemi- 

 cal basis for the statements of Mudie (1934) and Johnston 

 (1934) that the eating of garlic will cause the disappearance 

 of threadworms from the human digestive tract. Lapage 

 (193.S) suggested that compounds which yield H:S when sub- 

 .iectod to the action of intestinal bacteria might eventually be 

 used as anthelmintics. 



Some of the products of protein putrefaction, especially H2S, 

 rapidly combine with molecular oxygen and when in solution 

 produce very low oxidation-reduction potentials. Bergeim 

 (1924) devised a chemical method of obtaining an index of the 

 reducing power of intestinal contents, and he found that the 

 amount of reduction varied with diet. Preliminary electrical 

 measurements of the oxidation-reduction potential of the rat 

 digestive tract (Jahn, 1933) have shown that the Eh value may 

 be as low as — 200 mv. in the caecum and somewhat higher in 

 the lower small intestine. These measurements are well within 

 the "anaerobic" range and support the conclusions mentioned 

 above that oxygen is verj' scarce in the small intestine and ab- 

 sent in the caecum. 



The osmotic pressure of the digestive tract is usually some- 

 what higher than that of the serum and tissues. Schopfer 

 (1932) gives the following freezing point depressions for va- 

 rious animals: sheep, 0.70-0.83° C; cow, 0.80° C. ; horse, 0.74- 

 0.77° C; hog, 0.9-1.0° C; and the elasmobranch Scylliorhini/s, 

 2.4° C. With the exception of the elasmobranch the serum of 

 the above animals has a molecular depression of about 0.55 to 

 0.65° G. Davey (1936b) gave a value of 0.55-0.63° C. for the 

 abomasal contents of sheep. The osmotic pressure of the in- 

 testinal contents probably varies considerably with salt intake, 

 but absorption and excretion are apparently rapid enough to 

 prevent the osmotic pressure from ever becoming more than 

 twice that of the blood. As will be discussed below (General 

 Chemical Composition) the osmotic pressure of the medium 

 determines that of the worms. However, the effect of this 

 change in osmotic pressure on worm metabolism is unknown. 

 Davey (1938) has shown that Ostertagia circumcincta is capable 

 of living in NaCl which varied from .4 percent to 1.3 percent 

 (0.9 percent is equivalent to a freezing point depression of 

 0.6° C). In balanced salt solutions the range would probably 

 be greater. 



ANTIENZYMES 



Since the nematodes of the vertebrate digestive tract live in 

 a medium high in the concentration of proteolytic enzymes, the 

 question of how they are able to resist digestion has often been 

 mentioned in the literature. The mechanism seems to be at 

 least dual: (1) the cuticle is relatively indigestible, and (2) 

 the worms contain or secrete antienzymes, i.e., substances which 

 inactivate the digestive enzymes. Evidence for this latter 

 mechanism was first described by Weinland (1903) who de- 

 scribed a substance with antitryptie powers in aqueous extracts 

 of Ascaris. Dastre and Stassano (1904) believed that the ac- 

 tion was antikinasic, but the experiments of Hamill (1906) 

 confirmed the original conclusions of Weinland (1903). Hamill 

 (1906) ascribed the following properties to the antienzyme: 

 highly soluble in water and weak alcohol; insoluble in 85 per- 

 cent alcohol ; thermostable in neutral or acid solutions ; ther- 

 molabile in weakly or strongly alkaline solutions ; readily dif- 

 fusible through membranes which retain colloids. Harned and 

 Nash (1932) described an improved method for preparing high 

 concentrations of antitrypsin by fractional precipitation with 

 alcohol. They claimed that by varying the concentration of 

 alcohol a preparation of antitrypsin could be obtained almost 

 free of Ascaris protease. These investigators were able to 

 demonstrate that their antitrypsin preparation also contained 

 a weak antipepsin. A powerful trypsin inhibiting fraction was 

 also recently isolated by Collier (1941) from Ascaris. An anti- 

 trypsin with chemical properties similar to those of Ascaris 

 antitrypsin has been prepared from egg white by Balls and 

 Swens'on (1934). 



Sang (1938) investigated the mechanism of the action of 

 Ascaris antienzyme and confirmed the conclusion that the sub- 

 stance exerted both an antitryptie and an antipeptic activity. 

 However, he could not confirm the result of Harned and Nash 

 (1932) that the ratio of protease to antienzyme could be varied. 

 Sang concluded that Ascaris protease and Ascaris antitrypsin 

 and antipepsin are all one and the same substance, and he pro- 



359 



