CAPILLARIES. 



365 



It is perfectly natural to believe that this would be the result ; know- 

 ing, as we do, that every organ of the human body is both improved 

 and strengthened by careful cultivation. With our many excellent 

 contrivances for moderating the intensity of artificial light, when em- 

 ployed, there is, indeed, but small risk of injury to the eye. 



Capillaries are, with very few exceptions, always supported by an 

 areolar network, which serves not only as an investment to them, but 

 connects them in timately with the tissues they are destined to supply. 



No. 1 represents the fine network of air- tubes that supply the lungs with air. 

 No. 2 the network of capillaries for conveying blood to the lungs. 



There is a possibility, in first examinations, of mistaking or con- 

 founding capillaries with nerves, especially if the part under observation 

 should have been left for some time in the strong preserving or alka- 

 line solutions in the act of cleansing. A weak solution of caustic soda, 

 and also another of acetic acid, are both made use of : the first is more 

 generally available for the purpose of discovering nerves ; the latter in 

 tracing out vessels, structure of papillaB, unstriped muscle, &c. ; inas- 

 much as it renders their nuclei more obvious, while soda makes them 

 less so. It is very useful sometimes to use these re-agents alternately ; 

 and the rule is, to apply them to the object while under the microscope, 

 BO as to watch their gradual operation. 



It is not in the blood alone that cells float in a fluid ; the chyle and 

 lymph are but colourless corpuscles, flowing along their especially- 

 adapted ducts and tubes, and carrying the nutritive particles gathered 



