LAW OF INHERITANCE. 81 



As all animals deviate more or less from this perfect stand- 

 ard, we have every variety of organization. No two struct- 

 ures are exactly alike. If the principle "Like begets like" 

 applied to only one animal structure, its operations would be 

 simple and easily traced out. 



LAW or IXHERITAXCE. 



We have, then, two agents in which there is a great differ- 

 ence, not only in the development of individual organs, but 

 in whole classes, or in one of the temperaments, so called. 

 It is this union or combination of similar and dissimilar quali- 

 ties that the results or effects of inheritance must be estimated. 

 As a geriferal thing, the greater the difference the more marked 

 the results ; and, on the other hand, where there is great sim- 

 ilarity in the agents there will be sameness in results. The 

 great general law is based upon the perfection of the whole 

 organism, and the harmony of function in the operations of 

 every individual organ ; but in its application the law applies 

 to every kind and variety of structure. 



In some respects this law may be compared to the princi- 

 ples of gravitation, electricity, or chemical affinity where their 

 application is affected by or dependent upon the material upon 

 which they operate. In order to understand the nature of the 

 law or general principle, we must take into account all the 

 conditions that modify its operation. It is sometimes very 

 hard to do this. Nature does not always reveal her secrets. 

 In the early history of all the sciences, it has been found diffi- 

 cult, and has required a long time to remove, all obstruction 

 and doubt in the settlement of general principles ; but all this 

 toil and delay does not disprove in the least the existence of 

 such principles. 



It may be remarked that this whole subject of inheritance 

 or hereditary law is very imperfectly understood. It is true 

 a few individuals have given it some special attention. Some 

 have recorded the results of their experience and observation ; 

 but there are more who have acquired a great amount of prac- 

 tical information upon the subject, but made no record of the 

 same, so that those who came after them are but little, if any, 

 the wiser for it. Even in human physiology, where these 

 principles would natui*ally be considered of the greatest im- 

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