424 ADVANCED PHYSIOLOGY 



latter reach below the water level. Pour hydrochloric acid into the thistle 

 tube ; CO 2 is immediately formed, though slowly, and can be collected by 

 merely letting the gas run into the bottom of a jar ; the weight of the gas 

 will force out the air above it. Too free diffusion into the air should be 

 prevented by covering the jar with a glass plate ; see figure. 



10. Formula for fluid in which to preserve parts of central nervous 

 system so as to show white and gray regions : 



10 parts potassium bichromate 

 15-20 " formaldehyde (40%) 

 500 " water 



Let material stand in above mixture two weeks or so ; if not hard then, 

 place overnight in : 



2 parts 5% formalin 



1 " 95% alcohol (ethyl) 



A fresh brain placed in the last named mixture alone will harden in two 

 days ; but the regions of gray and white matter will not be differentiated. 



Chemical Composition of Various Substances Mentioned 

 in This Book 



Acetic Acid C 2 H 4 O 2 



Alcohol C 2 H 6 OH 



Ammonia NH 3 



Caffein 



Carbon Dioxid CO 2 



Fat (stearin) 



Glycogen C 6 Hi O 6 



Glycerin C 3 H 6 (OH)3 



Hydrochloric Acid HC1 



Milk Sugar Ci 2 H 22 Oii 



Proteid (egg albumin) 



Starch C 6 Hi O 6 



Sugar (grape sugar, glucose, etc.) C 6 Hi 2 O 6 



Urea CO(NH 2 ) 2 



Uric Acid C 6 H 4 O 3 N 4 



