ARRANGEMENTS OF FUNCTIONS. 243 



spends with the middle or muscular coat of the arteries ; and 

 accordingly, in vessels of somewhat greater size, the character- 

 istic circular fibres of that tunic appear in the layer in question 

 as well as the nuclei. Outside of all is the areolar coat, marked 

 by longitudinal nuclei. In vessels of l-60th of an inch in 

 diameter, or even less, the elastic layers of the inner coat may 

 be discovered, in form generally of fenestrated membrane, 

 more rarely of longitudinal reticulating elastic fibres ; while 

 the primitive membrane, with its longitudinal corpuscles, dis- 

 appears."* 



The vital properties of the capillaries form a subject of the 

 greatest importance, but too little settled to be given within a 

 short compass. 



The lymphatics and lymphatic glands have been already 

 noticed in some detail at p. 133. 



The serous membranes have also been reviewed at p. 94. 



The mucous membranes have also engaged a large share of 

 attention at p. 108. 



OUTLINE OF ASSIMILATIVE FUNCTIONS LESS DIRECTLY NUTRI- 

 TIVE, AS EXERCISED IN THE HIGHER ANIMALS. 



As it is hardly possible to obtain an intimate acquaintance 

 with the physiology of any system of living parts without a 

 general acquaintance with the whole animal economy, it seems 

 proper to exhibit a brief outline of the other principal functions 

 in the higher animals, by way of supplement to the special 

 subject of this treatise. 



Arrangement of the Functions as a whole. The functions 

 exercised by the higher animals are commonly arranged into 

 (1) functions of assimilation, (2) functions of reproduction, and 



* Sharpey in 'Quain's Anatomy,' vol. i. p. 231. 





