86 PHYSIOLOGY OF THE INVERTEBRATA. 



form, were washed in water, and tlien cleaned by means of a 

 brush. They were cut into small pieces and left to harden, 

 for twenty-four hours, in a large quantity of absolute alcohol. 

 Aqueous extracts (neutral, alkaline, and acid) were made of 

 the hardened pieces ; but each extract was found to be com- 

 pletely inactive as a digestiv^e fluid. Fibrin remained intact 

 in them during many days. 



These extracts had a milky appearance, due to an intense 

 fluorescence, which immediately suggested the presence of 

 glycogen. A solution of iodine (in water) converted these ex- 

 tracts into brown-coloured liquids. They formed a precipitate 

 in the presence of alcohol, which was dissolved by copper sul- 

 phate and potash. 



Finally, the addition of saliva caused the opalescence to 

 disappear, and at the same time the liquid became rich in 

 glucose, as proved by Fehling's solution. It must be dis- 

 tinctly understood that this glycogen is not present in the 

 internal fluids of the tape-worm's body, but is present in the 

 integument of that animal. Glycogen is also present in the 

 integument of the Ncmutoidca. 



It is seen from these investigations that the Ccstoidea, 

 and possibly the Trcmatoda as well, do not contain any traces 

 of digestive ferments, either pepsin, trypsin, or diastatic 

 ferment. 



The juices of the small intestine in which Tcvnia scrrata 

 lives are, nevertheless, rich in ferments ; but these ferments, 

 having little diff'usive power, do not pass the barrier which 

 the external skin of these Entozoa offers them. This was 

 proved in the following manner: — ^ovae Ascarcs marginatcc 

 (belonging to the Ncmatoidc(i), obtained from the small in- 

 testine of a dog, were placed, some intact and others cut 

 into pieces, into an artificial pancreatic juice.* Those which 

 were left intact remained in the juice without apparent 

 change; but those cut into pieces were almost completely 



* The aqueous extract of a dog's pancreas which had been hardened in 

 alcohol. 



