46 E7isheafhfd Larvae of Rome Parasitic Nernatoflefi 



after this length of time. Thirty per cent, saline and pure glycerine 

 produce strong plasmolysis and kill the larvae. 



Looss ((4) p. 439) quotes the results of Leichtenstern, Lambinet, Breton 

 and Boycott, who all tested the resistance of ensheathed Ancylostoma 

 larvae to the action of gastric juice, and found that the sheaths were 

 not affected in any way by the peptic ferment. 



These results show that the sheath is composed of a very resistant 

 substance and Martin speaks of it as chitinous in character. 



In my experiments I found that the sheaths of N. americanus, 

 G. strigosum and T. retortaeformis are insoluble in the following reagents : 

 water, alcohol, xylol, chloroform, phenol, lactophenol, formol, glycerine. 



The sheaths remain unaffected even after several days' immersion 

 in solutions of pepsin and trypsin, though the larvae within are ultimately 

 killed and show signs of disintegration. 



The sheaths are soluble in concentrated hydrochloric acid. Those of 

 N. americanus become dissolved in the course of 1| hours at room tem- 

 perature, whilst the sheaths of G. strigosum. and T. refortaeformis resist 

 the action for about 2| hours. It is of interest to note that chitin is 

 soluble in concentrated hydrochloric acid yielding glucosamine. 



Caustic soda, 5 per cent, solution, dissolves the sheaths and the en- 

 closed larvae at 37° C. when left in the incubator overnight, whilst a 15 

 per cent, solution dissolves the sheaths of all three kinds within 1;^- hours. 



The action of this alkali shows that the sheath substance is not real 

 chitin since the latter is prepared from insects, etc., by the prolonged 

 action of alkalis and repeated washings in water. 



The sheaths stain easily and uniformly with 1 per cent, solution of 

 methyl-green and fuchsin. I found that N. americanus larvae came out 

 of their sheaths, as found by Herman and confirmed by Looss, when 

 the drop containing the larvae and the stain is covered with a coverslip. 

 G. strigosum. and T. retortaeformis larvae did not exsheath. The sheaths 

 also stain a little with picric acid solutions. 



These results show that the sheaths are composed of some substance 

 of a resistant nature, but not so resistant as true chitin obtained from 

 various Arthopoda, Arachnida, Mollusca and Polyzoa, since they dis- 

 solve quite readily in 5 per cent, caustic soda. 



SUMMARY. 

 1. The eggs of Graphidium strigosum and Tricliostrongylus retortae- 

 formis give rise, under suitable cultural conditions, to larvae which finally 

 become ensheathed and wander from the culture medium. 



