308 JOHN W. SCOTT. 



The preceding experiment indicates the probable grave danger 

 that the parasite undergoes in passing through the dog's stomach. 

 It also illustrates the quick response that the bladderworm gives 

 to favorable or to unfavorable surroundings, and the response 

 itself is a reaction to a chemical stimulus. After a considerable 

 number of preliminary experiments in which the main facts of 

 this paper were established, I planned a more complete series, 

 one of which I shall give as typical of the entire set. The earlier 

 experiments were conducted at room temperature. 



First, I made up some solutions which contained the principal 

 elements of gastric and pancreatic juices, the formulae for which 

 have been given. Second, several solutions were prepared con- 

 taining different combinations of certain of these elements. In 

 most cases the solution had as nearly as possible the same 

 concentration of each component that is found in the natural 

 digestive fluids of the dog. This is shown in the third column of 

 Table I. Equal amounts of these solutions were next put in 

 stender dishes and six well-developed and carefully selected 

 cysticerci were placed in each solution. All stender dishes 

 were then placed in a large water-bath in which the temperature 

 varied less than one degree from 37^ C. I was unable to 

 examine this experiment until four hours and fifty minutes 

 later, and this allowed more time than is ordinarily required for 

 stomach digestion. The general results of this first examination 

 are given in the fourth column of the table. It will be noticed 

 that in lots 2, 3 and 10, in which hydrochloric acid alone was used, 

 there was not a single case of evagination in the eighteen speci- 

 mens. The same was true for lot I where sodium chloride was 

 used. The best result was produced by the artificial pancreatic 

 juice, lot 8, in which five out of six evaginated. The next best 

 results were found in the enzyme solutions, lots 4, 7, and n, 

 though the reaction to the alkaline solution of sodium carbonate 

 might be considered just as good, lot 6. The dishes were again 

 examined the next morning, 21 hours after the beginning. This 

 allowed considerably longer time than that required for complete 

 digestion, and therefore the results shown in the last column do 

 not come out in such contrast as they do when examined some- 

 what earlier. For subsequent work has shown that cysticerci 



