BISTRIBUTION OF CAPILLARIES. 



623 



436. A well-injected preparation should have its vessels com- 

 pletely filled through every part ; the pai'ticles of the coloring 

 matter should be so closely compacted together, that they should 

 not be distinguishable unless carefully looked for; and there 

 should be no patches of pale uninjected tissue. Still, although 

 the beauty of a specimen as a microscopic object is much im- 

 paired by a deficiency in the filling of its vessels, yet to the ana- 

 tomist the disposition of the vessels will be as apparent when 

 they are only filled in part,, as it is when they are fully distended ; 

 and imperfectly injected capillaries are better seen, when thin 

 sections are mounted as transparent objects, than are such as 

 have been completely filled. 



437. A relation may generally be traced between the disposi- 

 tion of the Capillary vessels, and the functions they are destined 

 to subserve ; but that relation is obviously (so to speak) of a me- 

 chanical kind ; the arrangement of the vessels not in any way 

 determining the function, but merely administering to it, like 

 the arrangement of water or gas-pipes in a manufactory. Thus 

 in Fig. 329, a, we see that the capillaries of fatty tissue are dis- 



Fia. 329. 



Capillary network around Fat-cells. 



Capillary network of Muscle. 



Distrihulion of Capillaries 

 in Mucous Membrane. 



Distribution of Capillary bloodvessels 

 in Sfcin of Finger. 



posed in a network with rounded m-eshes, so as to distribute the 

 blood among the fat-cells (§ 422); whilst at b we see the meshes 

 enormously elongated, so as to permit muscular fibres to lie in 

 them. Again, at c we observe the disposition of the capillaries 

 around the orifices of the follicles of a mucous membrane ; whilst 

 at D we see the looped arrangement which exists in the papillary 

 surface of the skin, and which is subservient to the nutrition of 

 the epidermis and to the activity of the sensory nerves. 



