EXPERIMENTS WITH TAPEWORMS. 307 



phosphate are found in such small amounts in gastric juice that 

 they were considered negligible. That they are not important 

 factors in this experiment was verified by the results. For a 

 similar reason diastase, potassium phosphate and lipase were not 

 included in the artificial pancreatic juice which I used. 



Two interesting questions had arisen in this connection: 



(1) Why is the young parasite not digested in the stomach? 



(2) What are the factors which influence or produce evagination? 

 The answer to the first question is that as a matter of fact some 

 of the cysticerci probably do meet the fate suggested, and that 

 all react negatively to the gastric juice in such a way that its 

 full effect is hindered or prevented. The answer to the second 

 question will come out as we proceed. 



In one of my experiments twenty cysticerci were removed from 

 their cysts and ten were placed in each of two stender dishes. 

 On these was poured a solution consisting of 0.4 per cent, of 

 hydrochloric acid in which was dissolved a small amount of scale 

 pepsin. Upon the addition of this liquid the bladderworms 

 contracted strongly, especially at the invaginated end, and 

 remained perfectly quiet, though they had previously been 

 somewhat restless. The room temperature was about 90 

 Fahrenheit. Within an hour the bladders were digested enough 

 so that they began to come apart. The cysticerci were left in 

 this solution three and one half hours, and in all this time they 

 showed no signs of activity, though the loose bladders were well 

 digested. The acid solution was then removed and replaced by 

 a solution containing the chief elements of artificial pancreatic 

 juice as described above, leaving out the pancreatin. Within 

 ten seconds several cysticerci had become active, and in a short 

 time a few of them had evaginated. They were restless, however, 

 and very soon all again drew in the scolex. Some pancreatin 

 was now added to the solution; by the time this was dissolved 

 most of the cysticerci were active and in the course of a few 

 minutes ten out of twenty specimens had evaginated, though 

 some of these had hardly completed the process. The dishes 

 were then left over night. The next morning all were completely 

 everted and most of them were relaxed in an excellent condition 

 for preservation or study. 



