178 PHYSIOLOGY CHAP. 



by diapedesis, and penetrate through the lacunae of the plasma 

 into the lymphatic system. 



Be this as it may, it is certain that diapedesis proceeds ' 

 tumultuously during inflammatory irritation, and gives rise to the 

 phenomenon of suppuration at the focus of inflammation. 



In order to complete the theory of corpuscular diapedesis we 

 must further inquire why the leucocytes become stationary and 

 adherent at the origin of the veins, and migrate from the vascular 

 system. A satisfactory answer to this question can only be 

 obtained from the interesting studies of Pfefier on Chemotaxis, 

 which were alluded to in Chap. III. (pp. 74-76). 



Leber was the first to regard the migration of leucocytes as 

 a chemotactic phenomenon, caused by an attractive or directive 

 action exerted by the chemical products of the pyogenic or pus- 

 producing microbes on the leucocytes. He extracted from -the 

 culture of Staphylococous pyoyenes aureus a crystallisable substance, 

 which he termed phlogosiu, and observed that some time after the 

 introduction of a capillary tube filled with a solution of this 

 substance into the anterior chamber of the rabbit's eye, a mass of 

 leucocytes migrated from the pericorneal vessels. 



Lubarsch was able to show that living bacteria had a greater 

 attraction for frog's leucocytes than those previously killed by heat. 



Massart and Bordet succeeded in showing that the same 

 leucocytes are attracted by liquid cultures of different microbes 

 (v. Fig. 19, p. 75, Stapliylococcus pyogenes albus), by inflammatory 

 exudates, and by certain nitrogenous or phosphorus-containing 

 waste products, e.g. leucin. They also discovered another im- 

 portant fact : if the leucocytes are narcotised in the total narcosis 

 of the animal by paraldehyde or chloroform, they are checked like 

 amoebae in their active movements, and all emigration that might 

 be going on from the vessels ceases entirely. This confirms the 

 idea that the migration of the leucocytes is a process dependent on 

 their excitability or amoeboid sensibility. 



In microscopic observations of the circulation in .small vessels and 

 capillaries, the transparency of the richly vascular organs of certain 

 animals can be made use of. This is excellently seen in the frog's lung, 

 by Holmgren's method (v. Fig. 48, p. 173). After cm-arising the animal l>y 

 the subcutaneous injection of a few drops of 1 per cent curare (sufficient to 

 paralyse it) a lateral incision is made through the whole depth of the 

 body wall, a little below the anterior limb. The lung inflated with air 

 will usually protrude of itself from the opening. To avoid emptying the 

 lung, which is useless for observation in the collapsed state, Holmgren 

 employed a small cannula, which is introduced through the glottis, and 

 attached by a ligature to the lower jaw. The end of the cannuJa has two 

 circular grooves in which is tied a bit of frog's intestine into which the 

 cannula had l>eeii introduced. Between the two grooves are two openings, 

 into which air is blown so as to distend the intestine drawn over it. This 

 dilates, and serves as a tampon, preventing the air of the lung from escaping 

 through the space between the cannula and the glottis. A small rubber tube 

 is fixed to the cannula, carrying at the other end a clip which is closed so 



