CAPILLARIES. 



553 



Fig. 289. The bronchi, a fine network of 

 air-tubes for supplying the lungs with air. 



the tissues they are destined to supply. A possibility arises, 

 in first examinations, of mistaking or confounding capil- 

 laries with nerves, especi- 

 ally if the part under 

 observation should have 

 been left for some time in 

 strong preserving or al- 

 kaline solutions. 



A weak solution of 

 caustic soda, and also 

 another of acetic acid, are 

 both of use ; the first is 

 available for the purpose 

 of tracing nerves; the 

 latter in making out 

 vessels, structure of pa- 

 pillae, unstriped muscle, 

 &c., inasmuch as it renders 

 their nuclei more obvious, 

 while soda thickens and 

 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 micro- 

 scope, so as to watch 

 their gradual opera- 

 tion. 



It is not in the 

 blood alone that cells 

 float in a fluid ; the 

 chyle and lymph are 

 colourless corpuscles, 

 flowing along their ** 

 especially - adapted 

 tubes and ducts, and 

 carrying the nutri- 

 tive particles gathered 

 from the food to the Fig * 290 - A 

 blood-vessels, for the 

 reparation of the framework, or growth that incessantly 

 goes on in the animal body. Fig. 272 d, represents the 



distributed 



