GENERATION OF ANIMALS, IV. iv. 



tions and deformations occur in respect of the inward 

 parts too ; animals either lack certain parts, or have 

 them in a mutilated form, or have too many of them, 

 or in the wrong places. No animal, it is true, has 

 ever been born without a heart, but there have been 

 animals without a spleen, and \%ith two spleens, and 

 Avith one kidney ; none without any liver at all, but 

 certainly with an incomplete one. These phenomena 

 are found in animals that are perfect " and living. 

 We find, also, animals with no gall-bladder which 

 naturally should have one * ; others with more than 

 one. Instances have occurred of organs in the 

 wrong places : the liver on the left side and the 

 spleen on the right. These things, as I said, have 

 been observed among animals which have reached 

 perfect growth ; among newly born animals in- 

 stances have been seen exhibiting great and varied 

 confusion. Those which depart only slightly from 

 the natural usually live ; those which depart more 

 than that do not — i.e., when their unnatural con- 

 formation lies in the parts that control the creature's 

 life. 



The point about these which we have to consider 

 is the following. Ought we to hold that one and the 

 same cause is responsible for the production of a single 

 offspring and the deficiency in the parts, and also for 

 the production of man)- offspring and the redundancy 

 in the parts, or not ? 



To begin, then, first of all, with the fact that some (b) Number 

 animals produce many offspring, others a single one °' ° =>pring. 

 only. Surely surprise at this is very reasonable, as it 

 is the largest of the animals which produce one only, 

 e.g., the elephant, the camel, the horse and those 

 with uncloven hoofs ; of these, some are larger than 



