306 JOHN W. SCOTT. 



Cysticercus tenuicollis. 'The parasite should be held just below 

 the head-cone in the finger and thumb of one hand, while a 

 regular pressure from within outwards is exerted with the fingers 

 upon the head-cone. The head-cone will lengthen and if the 

 manipulation is repeated several times, it will turn inside out 

 and will hang down as a flat, wrinkled, contractile band upon the 

 surface of the bladder. If pressure is now exerted upon the free 

 end, the head will finally become everted, springing out with a 

 sudden jerk." I have found the process of evagination is much 

 more difficult to produce in the smaller Cysticercus pisiformis, and 

 it is not believed that the contraction of stomach or intestine of 

 the host could have any important role worthy of consideration 

 in producing the eversion of the scolex. 



We must therefore look upon the process of eversion as a 

 response to chemical rather than to physical stimuli. For when 

 fed to a dog practically all cysticerci may evaginate under favor- 

 able circumstances. In young, previously uninfected, dogs the 

 percentage rose as high as 90 to 100 per cent, of infection. In 

 old dogs the percentage of infection is not so high. Whether this 

 is due to a sort of immunity dependent upon previous infection, 

 or to some change in the strength of the digestive juices, I am 

 unable to say. 



Since it is highly improbable that physical stimuli have any 

 important role in producing eversion, it was decided to try the 

 plan of stimulating these animals with artificial digestive juices. 

 The following formulae were used as a basis in preparing the 

 solutions used in these experiments : 



1. For artificial gastric juice: 



Water 100.0 parts 



Hydrochloric acid 0.2 (dog, 0.3-0.5 part) 



Pepsin o.i 



2. For artificial pancreatic juice: 



Water 100.0 parts 



Sodium chloride 0.6 



Sodium carbonate 0.2 (dog 0.4 part) 



Pancreatin 0.2 



My solutions did not include all of the elements found in the 

 natural product, but the calcium chloride and the potassium 



