CEBEBBAL EXCITANTS. 117 



the eye, larynx, in neurotomy, etc. ; also to detect ob- 

 scure lameness. As a mydriatic it is much more 

 serviceable than atropine. Has been given in con- 

 valescence from fevers and protracted illness, in doses 

 of grs. i.-v. to the horse; for the dog, gr. ^1. For 

 local anaesthetic effect upon the horse, inject hypo- 

 dermically from gr. v.-xv. occasionally more is re- 

 quired. Its effect begins in about tvi^enty minutes 

 and continues for from one-half to two hours ; maxi- 

 mum, in about one hour. If kept in solution, add 

 •j-^ part of boric acid to prevent decomposition. 



Caffeina — Caffeine ; Theina — Theine. 



Caffeine and theine are now generally conceded to 

 be identical; the former is obtained from the dry 

 seeds of Coffea Arabica (the coffee tree), the latter 

 from the dry leaves of Thea sinensis (the tea plant) . 

 They are also found in other plants. Caffeine occurs 

 as white, shining, elastic needles, soluble in 80 parts 

 of water, 50 parts of alcohol, and in 9 parts of chloro- 

 form. It is a cardiac tonic and diuretic, and is used 

 as a substitute for digitalis, which it occasionally 

 effectually replaces. It is in medicinal doses also a 

 stimulant to the nerve centres in the cerebrum, me- 

 dulla, and cord ; but over-doses paralyze. It regulates 

 the heart's action, and causes the removal of oedema 

 by increased diuresis. It is rapidly absorbed, rapidly 

 eliminated, and has no cumulative effects. It is best 

 given hypodermically with sodium salicylate, which 

 increases its solubility and activity. Dose: H., gr. 

 v.-xx. ; D., gr. i— 2. 



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