256 GENERAL ANATOMY. 



The blood becomes nevous in the general capillary system, 

 and arterial in the pulmonary capillary system. 



382. The sanguineous capillary vessels, such as they have 

 just been described, are not equally abundant, and have not 

 the same volume in all the parts of the body. The amount 

 of the vessels of each part may be esteemed by the redness 

 that it acquires when congested or inflamed, as well as when 

 it is injected : this latter method is even preferable. The most 

 successful injections made, are those of Ruysch, Albinus, Lie- 

 berkuhn, Earth, Bleuland, Soemmering, and Prochaska. 



The injections of Ruysch, by filling the most minute vessels, 

 gave rise to the opinion that the whole of the solid substance 

 of the body is vascular. Ruysch himself, however, acknow- 

 ledged, that there were in the body parts more or less vascu- 

 lar, and others were entirely deprived of vessels. Albinus, 

 in examining injected parts while yet fresh, and also when 

 dried, observed that even after the most successful injections, 

 there remains always more or less substance which was not 

 reached by the injection, according to the nature of the parts: 

 he thus controverted an erroneous opinion, which had espe- 

 cially arisen from the examination of the parts while dried or 

 macerated, so as to cause the parts which can not be injected 

 to disappear, or to be destroyed. 



Microscopical observations and different experiments on 

 living bodies also show, that there are parts more or less vas- 

 cular. Thus, if the mesentery or the webs of the feet of a 

 living frog be examined with the microscope, we shall see 

 that the most minute capillary vessels, those which admit only 

 one globule, are separated by a considerable space, whilst in 

 the pulmonary mucous membrane of the same animal it would 

 be impossible to stick a very fine needle without opening se- 

 veral of these vessels; nor is there, on the surface of the skin 

 of a living man, a point in which a needle would not produce 

 the same effect; while in the ligamentous parts, in the nervous 

 substance, in the cellular tissue, &c. considerable divisions 

 may be made without causing a drop of blood to issue. 



If all the solid parts were vascular, and entirely vascular, 

 there would be no longer any difference between them, all 



