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CHAPTER II. 



FUNCTIONS. ANIMAL MOTIONS. MOLECULAR MOTION. ORGANIC 



MOLECULAR MOTION. MUSCULAR MOTION. CILIARY MOTION. 



MOTIONS OF SPERMATOZOA. 



THE subdivision of the functions of the human organism into 

 the animal and the organic, as already stated, may be adopted as 

 the least objectionable basis for their arrangement. Under the 

 former title we include those functions, which are peculiar to and 

 characteristic of the animal part of the living creation, and to which 

 there is nothing similar or analogous in the vegetable kingdom. 

 These are locomotion and innervation. The organic functions are pre- 

 sent in both kingdoms, \nth certain modifications. They are diges- 

 tion, absorption, circulation, respiration, secretion, and generation. 



In examining these various processes, we propose to follow the 

 order in which they have been enumerated. We find it con- 

 venient to take the locomotive function first, because so large a 

 proportion of the mechanical arrangements, or of the anatomy of 

 the body, is connected with it. The transition from locomotion to 

 innervation is easy and obvious; for the nervous system has a 

 special connexion with the locomotive organs, in order that the 

 influence of the will may be conveyed to them. It may be here 

 stated, that in the animal functions the interference of volition is 

 more frequent than in the organic ones ; and that, in all, the ner- 

 vous system exerts a certain control, and may influence to a great 

 degree the performance of the functions, although some of them are 

 essentially independent of it. 



Of the minute Movements occurring in the Interior of the Body. 

 Of these we may distinguish three kinds : 1. Those in which par- 

 ticles are moved passively by forces independent of themselves. 

 2. Those accompanying the incessant changes of the organic 

 elements of the tissues. 3. Those which occur in certain entire 

 tissues on the application of an appropriate stimulus. All these 

 movements may be called molecular, on account of the minuteness 

 of the particles concerned in them. 



1. The term molecular motion was used many years ago by Mr. 

 Robert Brown, to denote a phenomenon which he had witnessed 



