664 



PHYSIOLOGY. 



(hydraemia) causes an increased flow in conse- 

 quence of the purely mechanical rise of pressure 

 in the liver capillaries, this rise being ascertained 

 by taking simultaneous tracings of the blood 

 pressure in the portal vein and the inferior vena 

 cava. Many lymphagogues act by causing hy- 

 draemia, and in these the flow of lymph must 

 be directly caused by the increase in the portal 

 capillary pressure. That the lymph under these 

 circumstances comes from the liver is shown by 

 the absence of the flow from the thoracic duct 

 when the lymphatics of the liver are ligatured. 

 Some lymphagogues, the action of which was 

 specially noted by Heidenhain (such as crawfish 

 muscle extract), stimulate the flow of lymph 

 without giving any evidence of increased pres- 

 sure in the portal capillaries. The effect of these 

 lymphagogues disappears after long-continued 

 obstruction of the aorta, and on this ground, 

 since the liver lymph still flows, the author con- 

 cludes that lymphagogues of this class act on 

 other lymph sources than the liver, and proba- 

 bly in the main upon those present in the in- 

 testines. 



In his experiments on the flow of lymph from 

 the hind limbs, Dr. Lazarus Barlow found no in- 

 crease in the flow when considerable though in- 

 complete venous obstruction was maintained for 

 one hour, while the specific gravity of the blood, 

 muscles, and skin showed no evidence of any in- 

 creased exudation. Such increased flow and 

 exudation occurred, however, when, after dam- 

 ning up the katabolic products, the tissues under 

 observation were supplied with blood through 

 actively dilated arterioles. The dilatation, when 

 caused by section of the sciatic nerve, led to no 

 such increased exudation ; hence the author con- 

 cluded that the demands of the tissue are an 

 effective factor in lymph formation. When the 

 arteries are actively dilated the amount of exu- 

 dation varies directly as that of the venous pres- 

 sure : so that lymph formation, though not a 

 purely mechanical process, is nevertheless sim- 

 pler than a pure secretion, such, for instance, as 

 exists in the salivary glands. 



Having made a careful and critical study of 

 previous researches into the nature of the germi- 

 cidal constituents of blood serum, and experi- 

 menting with serum obtained from healthy dogs 

 and rabbits, Drs. Vaughan and McClintock 

 (" Medical News," Philadelphia), concluded that : 

 (1) The serum albumen is not the germicidal 

 substance in blood serum. (2) The germicidal 

 substance must belong to the proteids. otherwise 

 it would be difficult to explain the fact that a 

 temperature of 55 C. renders blood serum in- 

 active. (3) The only proteid likely to be pres- 

 ent in blood serum and which is not destroyed 

 by peptic digestion is nuclein. Having reached 

 these conclusions the following questions natu- 

 rally present themselves : 1. Is'there a nnclein in 

 blood serum ? 2. Has this nuclein, if there be 

 one, germicidal properties? These questions 

 Drs. Vaughan and McClintock have attempted 

 to answer. They found that blood serum con- 

 tains a nuclein having marked germicidal prop- 

 erties, and that the germicidal constituent of 

 blood serum can be isolated. 



It was shown by Dr. Vaughn ITarley, in 1893, 

 that the intravenous injection of grape sugar 

 caused an increase in the lactic acid in the cir- 



culation. It appeared probable that the lactic 

 acid, having driven out the carbonic acid, had 

 combined with the bases of the carbonates in 

 the blood. Experiments have since been made 

 to see what changes were produced in the gases 

 of the blood after the intravenous injection of 

 sugar. It was .found that the quantity of car- 

 bonic acid was diminished in the most marked 

 degree during the first hour after the sugar in- 

 jection, and still somewhat so from three to five 

 hours later. These results support the view 

 that the lactic acid drives the carbonic acid 

 from the sodium salts and replaces it. Next, the 

 changes in the quantity of oxygen in the blood 

 were investigated. It was found that oxygen 

 was diminished to a marked degree during the 

 first hour after the sugar injection. During 

 the third and fifth hours the quantity in arterial 

 was that usually found in venous blood. No 

 explanation is known for this condition. 



In his researches on the clotting of blood Dr. 

 Lilienfeld has succeeded in separating Al. 

 Schmidt's fibrinogen into 2 substances, throm- 

 bcsin and an albumose. The former unites with 

 calcium and forms fibrin, while the albumose 

 retards clotting. The separation of fibrinogen 

 into these 2 constituents may be brought about 

 by means of acetic acid, nuclein, nucleic acid, 

 and other substances. Blood clotting, accord- 

 ingly, consists in a disintegration of leucocytes, 

 setting free nuclein ; the latter then decomposes 

 the fibrinogen, and enables the thrombosin to 

 unite with the calcium salts of the blood. While 

 the blood is circulating in the body it contains 

 no free nuclein in solution, and hence clotting is 

 impossible. The author further considers that 

 peptones (albumose) and leech extract prevent 

 clotting by themselves uniting with the calcium 

 of the blood and thus preventing its union with 

 thrombosin. 



The researches of Heidenhain and Lehmann 

 point to the existence of weak non-diffusible 

 acid bodies in the serum and the corpuscles of 

 the blood which combine with large quantities 

 of alkali in a form that is capable of being easily 

 destroyed by carbon dioxide. One of the princi- 

 pal bodies is haemoglobin, which therefore plays 

 an important part in regard to the absorption of 

 oxygen and the maintenance of the alkalescence 

 of the blood. 



An account is given, in a paper by Prof. Heger 

 on the unequal diffusion of poisons into the organs 

 of the body, of some of the chief means by which 

 the organism continually struggles against toxic 

 substances, the principal objects to be effected 

 being the elimination of the unaltered poison, 

 its neutralization, or its destruction. The neu- 

 tralization may be a true chemical combination, 

 as in the case of carbonic acid, or a physical 

 localization in some special organs that can en- 

 dure the excess, so removing it from the rest of 

 the organism. Thus morphine, if given in a 

 series of increasing doses, accumulates in the 

 liver, spleen, and marrow of the bones. In the 

 case of rnicrobic poisoning, the author, while ad- 

 mitting the constant multiplication of the poison 

 by phagocytosis, etc., pointed out that some such 

 process of neutralization as that referred to is a 

 possible, and even a probable, antecedent to this 

 destruction. Thus the liver cells and their secre- 

 tion or extract appear to have exceptional anti- 



