INTEODUCTJON. 77 



be by suhcutaneous injection. The syringe for this pur- 

 pose (see Fig. 11) is small, and can conveniently be 

 carried in the pocket ; has its barrel graduated^ and made 



Fig. 11. — Hypodermic Syringe. (Armatage.) 



of glass ; generally has a handle to its piston, every complete 

 turn of which expels a known quantity of the contents, and 

 a nozzle shaped like a trocar with a side opening of exit. 

 The puncture is scarcely noticed by the animal, and 

 should preferably be made where the subcutaneous areolar 

 tissue is plentiful and the skin thin. By this means ex- 

 tremely small doses of very potent agents may be given 

 with certainty. We must conclude, then, that methods of 

 administration to the ox are seldom other than by drench. 



M. Tahorin estimates the dose for the ox to average |ths 

 that requisite for the horse, but specific differences be- 

 tween the animals, as far as the actions of different agents 

 go, render this useful conclusion not always reliable. He . 

 also reckons the ox^s dose three times as large as that for 

 the sheep. • 



Hertwig suggests for an animal aged one to two years 

 half a dose, six months to one year one quarter, three to 

 six months one eighth, and one to three months one 

 sixteenth. Pregnancy and lactation and other conditions 

 also influence the dose, and we must remember that 

 many agents administered to the cow pass off by the 

 milk and affect the calf. 



It is thought that all '^ agents which produce their 

 effects upon remote parts of the system must be absorbed 

 and added to the blood.'' The phenomena of certain 

 cases of poisoning hardly enable us to accept this dictum 

 unreservedly. When very large doses have been taken 



