30 STRUCTURAL COMPOSITION OF HUMAN BODY. 



contents are therefore quite cut off from the direct influence 

 of any motive power from without. The motion of the 

 particles, moreover, in a circuit around the interior of the 

 cell, precludes the notion of its being due to any other 

 than those molecular changes which we call vital. Again, 

 in the lowest animals, whose bodies resemble more than 

 anything else a minute mass of jelly, and which appear 

 to be made up almost solely of this albuminous protoplasm, 

 there are movements in correspondence with the needs of 

 the organism, whether with respect to seizing food or any 

 other purpose, which are unaccountable according to any 

 known physical laws, and can only be called vital. In 

 many, too, there is a kind of molecular current, exactly 

 resembling that which is seen in a vegetable cell. 



In the higher animals, phenomena such as these are so 

 subordinate to the more complex manifestations of life that 

 they are apt to be overlooked ; but they exist nevertheless. 

 The mere nutrition of each part of the body in man or in 

 the higher animals, is performed after a fashion which is 

 strictly analogous to that which holds good in the case of 

 a vegetable cell, or an animalcule ; or, in other words, the 

 life of each anatomical element in a complex structure, as 

 that of the human body, resembles very closely the life of 

 what in the lowest organisms constitutes the whole 

 being. For example, the thin scaly covering or epidermis, 

 which forms the outer part of a man's skin, is made up of 

 minute cells, which, when living, are composed in part of 

 protoplasm, not to be distinguished from that of a vegetable 

 cell or an animalcule, and which are continually wearing 

 away and being replaced by new similar elements from 

 beneath ; and this process of quick waste and repair could 

 only take place under the very complex conditions of 

 nutrition which exist in man. One working part of the 

 organism of an animal is so inextricably interwoven with 

 that of another, that any want or defect in one, is soon or 

 immediately felt by the whole ; and the epidermis which 



