ATTENTION TO CROSSING. 



115 



mention many improvers who were of the firsL class 

 formerly, but who are now only in the second.*' 

 Changes, in fact, by crossing are not to be effected in a 

 short space of time ; you must look forward to several 

 years of constant exertion, before you can hope, in this 

 manner, to alter your stock.* Then, again, we must 

 be aware of the tendency which nature, in numerous 

 instances, displays to perpetuate diseases, dispositions, 

 and abberrations from the normal structure. Many 

 qualities and diseases, are known, in man, to be heredi- 

 tary ; of the former, I may instance peculiarities in 

 walking, and writing; a passion for intoxicating liquors, 

 and other habits too trivial to mention ; and of the latter, 

 gout, pulmonary consumption, and blindness from 

 cataract, which are well known to harass a family for 

 generations. Features, in like manner, may remain 

 for ages of the same undeviating cast ; thus the Jews 

 of to-day are the very counterparts of the Jews of three 

 thousand years back, and, in all likelihood, will so 

 remain till the end of time. A predisposition to many 

 diseases is engendered in the sheep, by too great a re- 

 finement in breeding, which tends to diminish the size 

 of the animal, prevents them feeding to perfection, de- 

 stroys their fecundity, and imparts great tenderness of 

 constitution. Accidental deviations from the natural 

 type may, also, be hereditary, as is seen in those races 

 of dogs which have a supernumerary toe on the hind 

 foot, and tarsal bones to correspond. In the human 

 race also several generations of a particular family 



* Dr Stuim, professor of Agriculture, at Bonn, says, that a new 

 race may be produced in the same number of years as are required for 

 perfecting the teeth. 



