68 BORDER LINES OF KNOWLEDGE 



and inert, mostly because insoluble, substances. The 

 food of one animal or of one human being is some- 

 times poison to another, and vice versa; inert sub- 

 stances may act mechanically, so as to produce the 

 effect of poisons ; but this division holds exactly 

 enough for our purpose. 



Strictly speaking, every poison consisting of assimi- 

 lable elements may be considered as unwholesome food. 

 It is rejected by the stomach, or it produces diarrhoea, 

 or it causes vertigo or disturbance of the heart's ac- 

 tion, or some other symptom for which the subject 

 of it would consult the physician, if it came on from 

 any other cause than taking it under the name of 

 medicine. Yet portions of this unwholesome food 

 which we call medicine, we have reason to believe, 

 are assimilated ; thus, castor-oil appears to be par- 

 tially digested by infants, so that they require large 

 doses to affect them medicinally. Even that deadliest 

 of poisons, hydrocyanic acid, is probably assimilated, 

 and helps to make living tissue, if it do not kill the 

 patient, for the assimilable elements which it contains, 

 given in the separate forms of amygdalin and emulsin, 

 produce no disturbance, unless, as in Bernard's ex- 

 periments, they are suffered to meet in the digestive 

 organs. A medicine consisting of assimilable sub- 

 stances being then simply unwholesome food, we un- 

 derstand what is meant by those cumulative effects of 

 such remedies often observed, as in the case of digi- 

 talis and strychnia. They are precisely similar to the 



