70 BOARD OF AGRICULTURE. 



velopment to hereditary causes. Even such as are usually heredi- 

 tary are sometimes produced accidentally, (as of course there must 

 be a beginning- to everything-,) an'd in such case, they may, or may 

 not be, transmitted to their progeny. As before shown, it is cer- 

 tain that they sometimes are, which is sufficient reason to avoid 

 such for breeding purposes. It is also well known that in the 

 horse for instance, certain forms of limbs predispose to certain 

 diseases, as bone spavin is most commonly seen where there is a 

 disproportion in the size of the limb above and below the hock ; 

 and others might be named of similar character ; in all such cases 

 the disease may be caused by an agency which would be wholly 

 inadequate in one of more perfect form, but once existing, it is 

 liable to be reproduced in the offspring — all tending to show the 

 great importance of giving due lieed in selecting breeding animals 

 to all qualities, both external and internal, so long as "like produces 

 like." 



Law of Variation. — We come now to consider another law, by 

 which that of similarity is greatly modified, to wit, the law of vari- 

 ation or divergence. All organic beings, whether plants or ani- 

 mals, possess a certain flexibility or pliancy of organization, ren- 

 dering them capable of change to a greater or less extent. When 

 in a state of nature variations are comparatively slow and infre- 

 quent, but when in a state of domestication they occur much 

 oftener and to a much greater extent. The greater variabilit}'^ in 

 the latter case is doubtless owing, in some measure, to our domestic 

 productions being reared under conditions of life not so uniform, 

 and different from, those to which the parent species was exposed 

 in a state of nature. 



Flexibility of organization in connexion with climate, is seen in 

 a remarkable degree in Indian corn. The small Canada variet}^, 

 growing only three feet high and ripening in seventy to ninety daj's 

 when carried southward, gradually enlarges in the whole plant 

 until it may be grown twelve feet high and upwards, and requires 

 one hundred and fifty diiys to ripen its seed. A southern variety 

 brought northward, gradually dwindles in size and ripens earlier 

 until it reaches a type specially fitted to its latitude. 



Variation, although tlie same in kind, is greater in degree, among 

 domesticated plants than among animals. From the single Avild 

 variety of the potato as first, discovered and taken to Europe, liavo 

 sprung innumerable sorts. Kemp, in his work on Agricultural 

 Physiology, tells us, that on the maratime cliffs of England, there 



