53 



nually increased in number and size. The solid sub- 

 stance of the wood, and the temporary tender blossoms, 

 are alike extracted from that circulating fluid. If the 

 constituents for these are wanting, or if improper com- 

 ponents are introduced, or if the sap is too watery, dis- 

 ease is the necessary consequence. Disease, which in 

 youth and manhood usually arises from intemperance 

 and over-excitement, visits old age as a consequence of its 

 decayed vital powers ; and, "if the silver chord has not 

 been loosed," or "the golden bowl broken," by the 

 short-sighted indulgence of early years, man gradually 

 declines into the grave, as the vital organs cease to per- 

 form their office, because the limit of existence natural 

 to his species has been attained. Some diseases pecu- 

 liar to old age are prematurely induced in the usually 

 vigorous period of life by licentious indulgences, in- 

 dividual or hereditary. Ossification of the vascular 

 system is an example. In the vegetable part of the 

 creation, the canker or ulcer, to which our apple, 

 pear, elm, and other trees are subject, is a somewhat 

 parallel instance. This disease is accompanied by 

 different symptoms, according to the species of the 

 tree which it infects. In some of those whose true 

 sap contains a considerable quantity of free acid, as in 

 the genus Pyrus, it is rarely accompanied by any dis- 

 charge. To this dry form of the disease it would be 

 well to confine the term canker, and to give it the 

 scientific name of Gangrcena sicca. In other trees, 



