318 



COW-TREES. 



in an old plant amounts to nearly two-thirds of the 

 entire weight of the plant. When recent, it very 

 much resembles milk, and when consolidated it is 

 Indian rubber. 



It is not very clearly ascertained to which of the 

 two families the Palo de vacca, or cow-tree of South 

 America, belongs ; but the people resort to that tree, 

 fetch the juice in pitchers, and use it for the same 

 purposes as animal milk. Nor is it a little curious 

 that, in those parts of the world where, on account 

 of the parching up of the grass, the milk of domestic 

 animals is not so easily procured as in more tem- 

 perate climates, there should be an abundant, and by 

 no means a bad, substitute in the juices of trees. 



But besides their eatable juices, these plants have 

 a very deleterious principle, which in some of the 

 species is a very virulent poison. That principle is 

 Strychnia, so called from being first found in the 

 kernels of the Strychnos nux vomica and Strychnos 

 ignatidna ; but it is also found in the Upas, and in 

 other species : and it is not a little remarkable, that 

 while some of the species of Strychnos are so 

 deadly, others are valuable medicines. These co- 

 incidences in some respects, and differences in others, 

 should teach us to be cautious in not generalizing to 

 any of those artificial tribes of organized being any 

 property which we have discovered only in some 

 members of that tribe. The products of organi- 

 zation are quite different from both mechanical and 

 chymical results. We cannot repeat one of them, 

 and therefore we can never safely say that any one 

 of them has a property, unless that property has ac- 

 tually been discovered in it. 



Still the poison, or the other active matter that 

 may be in the plant, is well worthy of our study ; 

 because, generally speaking, it is in the plant itself, 

 and not in the food of the plant. In whatever part 

 of the plant it may ultimately be found, whether in 

 the root, as in the jatropha ; in the juice, as in the 



