392 BIOLOGY. 



As the gills were converted into lungs, a special body or 

 the thorax originated for them, which encroached upon 

 the abdomen. Now, the abdominal wall left between 

 these two cavities, was just the diaphragm. 



2259. The diaphragm is not a transverse wall or 

 septum. The idea of such a cross-rail gainsays all sound 

 physiology. It has been the abdominal wall. 



2260. The union of the lungs with the nervous sys- 

 tem is the nose. 



2261. The nose is the cephalic thorax; but it has 

 also the thoracic contents, or the very lung repeated in 

 itself. 



2262. The multicavernous ethmoid bone is the lung in 

 the nose, the two nostrils being the stigmata or foremost 

 openings of the trachea. The nasal muscles are homo- 

 logous to the cartilages of the trachea, and especially to 

 those of the larynx. 



2263. The velum palati is the diaphragm between 

 nose and mouth, or between the cephalic thorax and the 

 cephalic abdomen. 



Coverings. 



2264. The animal coverings are desiccated respiratory 

 organs appertaining to the integument. 



Capillary Vessels. 



2265. The principal function of the vessel is that of 

 secretion, whereby nutrition is imparted. This secretion 

 must take place in the whole body, in so far as it is op- 

 posed to the lung. The vessels then pass over into the 

 finest canals, and are called capillary vessels. 



2266. The capillary system of vessels is an organ in 

 antagonism to the lung ; what enters the latter organ, 

 passes out through the former. 



2267. The capillary system of vessels is the property 

 of the tegumentary system. It may almost be said that 

 wherever there is integument, there capillary vessels are 

 present. The most perfect evolution of capillaries is the 



