488 PHILOSOPHICAL TRANSACTIONS. [aNNO 1788. 



there is a method in the deviations of nature, so that they may be marked or 

 noted, the same varieties occurring in ditFerent animals. 



It cannot be at all important to the function of a viscus, whether it be in one 

 mass, or in separate portions. The structure being the same, the same action 

 will take place. Hence we often find the 2 kidneys joined together, forming one 

 mass; and not unfrequently 2 or 3 spleens, besides the common one. Neither 

 can it be important whether a viscus should always be of the same shape, because 

 its functions do not depend on shape, but on structure: we find accordingly, in 

 this particular, much variety. 



There are many of the viscera which arexonnected together in their functions, 

 or by the junction of large blood vessels, in such a way as to require nearly the 

 same relative situation among themselves. This becomes also necessary in order 

 to preserve the general shape of the animal. Accordingly we find, that when 

 any important viscus is changed in its situation, it aflfects the situation of other 

 viscera, requiring in them a similar change. We saw in the person who is the 

 subject of this paper, that a change in the situation of the heart and liver was 

 accompanied with a change of situation in the stomach, spleen, pancreas, and in 

 short the whole abdominal viscera. This however is a great deviation in nature; 

 for it is nothing less than changing almost the whole vital system in an animal, 

 and therefore it rarely happens. In such a change it does not appear that the 

 functions can be affected, as they depend on structure and situation, which are 

 both preserved. Hence the person who is the subject of this paper arrived at the 

 age of maturity, and might have continued to live to an extreme old age. The 

 human machine might have been constructed in this way generally, and under 

 such circumstances, what is now called the natural situation of parts would have 

 been as singular as the present phaenomenon. 



There appears to be less variety in the nervous system of animals of the same 

 species, than in most parts of the body. There is scarcely any difference in the 

 appearance of the brain, and much less in the distribution of the nerves than of 

 the blood vessels. There is also little variety in the organs of sense: perhaps the 

 mechanism in both these is nicer, so that a considerable deviation would inter- 

 fere with their peculiar functions. The most common great deviations which 

 nature produces in the structure of an animal, are various kinds of monstrosity, 

 by which the animal becomes often unfit for continuing its existence. Why 

 nature should in its greater deviations fall into a very imperfect formation, much 

 below the standard of her common work, does not appear very obvious. It 

 seems that there might have been many varieties where the functions could have 

 been preserved. Perhaps it is with a view to check the propagation of great va- 

 rieties, so as to preserve a uniformity in the same species of animals. 



It has been much agitated, whether monstrosities depend on the original for- 



