158 



the fat into the cells of the cellular tissue, furnish the urine tp the kid- 

 neys, and the liver with the materials of the bile : in a word, suffer to es- 

 cape, through the porosities with which their pa^ietes are pierced, the 

 principles which the blood has to furnish to every organ. 



It is by these lateral porosities, and not by extremities open on all the 

 surfaces, and in all the points of the organs, that the capillaries transpire, 

 in some sort, the elements of nutrition, and of the various secretions*. 

 Mascagni was aware, that Nature, skilful in deducing many effects from 

 few causes, has not deviated, in the construction of the system of circu- 

 lation, from the invariable laws of her ordinary simplicity; but the lateral 

 pores of the capillaries, which are sufficient for the explanation of all the 

 phenomena ascribed to the exhaling mouths of the arteries, and to the 

 pretended continuity of these vessels with the excretory ducts of the or- 

 gans, Sec. are not openings like the |)ores common to all matter; each of 

 them may be considered as an orifice, sensible, and, especially contractile, 

 of differing size, according to the state of the strength, or of the vital pow- 

 ers. The size then of these capillary pores is subject to frequent varia- 

 tions; and this is the explanation given of the formation of scorbutic ec- 

 chymoses, of petechiae, of passive or relaxed hemorrhages. In all these 

 affections, contractility being really diminished, the pores of the capilla- 

 ries enlarge, and suffer the red blood to transude through their relaxed 

 mouths. This phenomenon takes place, not only under the skin and on 

 the various mucous surfaces, it is observed also in the very tissue of the 

 organs. It is thus, that I have often seen, on opening the bodies of those 

 that had died of the scurvy, in its last stage, the muscles of the leg filled 

 with blood. This sort of interior hemorrhage, converts the muscles into 

 a kind of pulp; and the extravasated blood itself undergoes a beginning 

 of decomposition. 'I he bones themselves are liable to these scorbutic 

 bloody nitrations. I had an opportunity of ascertaining this in the Hos- 

 pital of St. Louis, at the same time that I learnt the difficulty of procuring 

 a durable skeleton from such bodies. The greatest number die, in a very 

 advanced stage of the disease, and the bones dissolve in maceration, or 

 rot in a very little time. 



The capillary vessels, whether the blood flow through them red, or 

 colourless, are not a system of vessels distinct from that of the arteries, 

 and from that of the veins: they belong essentially to these two orders of 

 vessels. Those which, ramifying in the tissue of the skin, or of the se- 

 rous membranes, suffer the serum of the blood to transude, are not more 

 entitled to the name ofexhalent system, which some authors have given 

 them. To consider a? distinct and insulated systems, separate parts of a 

 system of organs, is to incumber science with a crowd of divisions, as 

 false as they are useless. 



LXI. The sanguineous capillaries anastomose, and form, like the lym- 

 phatic capillaries, a net-work that envelopes all the organs. Their fre- 

 quent communications do not allow obstructions to take place, and to 

 produce inflammation, as Boerhaave thought, and as was long taught, on 

 the authority of that celebrated physician- Haller, Spallanzani, all the 

 microscopic observers, have perceived threads of blood flowing in the ca- 

 pillaries, offering themselves at the various inosculations of these vessels, 



* See APPENDIX, Note S, for observations on the functions of the capillary system ; 

 Jtnd on nutrition. 



