PLASMA OF THE BLOOD. 259 



the liver and the kidneys this disappearance is so complete that no 

 fibrine is to be obtained, as a general rule, from the blood of the renal 

 or the hepatic veins. On this account, also, the blood in the large veins 

 near the heart is more deficient in fibrine than in those at a distance ; 

 since the venous blood coming from the general circulation, and con- 

 taining a moderate quantity of fibrine, is mingled, on approaching the 

 heart, with that of the renal and hepatic veins, in which the coagulating 

 material is entirely absent. 



The albumen of the plasma is undoubtedly the most important of its 

 ingredients in regard to the process of nutrition, since it is by far the 

 most abundant of the albuminous matters present. It coagulates at 

 once on being heated to 72 (162 F.), or by contact with alcohol, the 

 mineral acids, or their metallic salts, or with potassium ferrocyanide in 

 an acidulated solution. It exists naturally in the plasma in a fluid form 

 by reason of its union with the water. The greater part of the water 

 of the plasma being united with the albumen, when this latter substance 

 coagulates, the water remains in combination with it, and assumes at 

 the same time the solid form. If the plasma of the blood, accordingly, 

 after removal of the fibrine, be exposed to a boiling temperature, it 

 solidifies almost completely, so that only a few drops of water can be 

 drained away from the coagulated mass. The earthy phosphates are 

 also retained by the solidified albuminous mass. 



The substance existing in the blood plasma, however, and designated 

 as albumen, appears to consist really of two different ingredients, of 

 which one is about double the quantity of the other. Both of them are 

 coagulable by heat ; and on this account the whole albuminous ingredient 

 of the plasma solidifies when exposed to a boiling temperature. But one 

 of them is coagulable also by magnesium sulphate added in excess. 

 This substance is termed metalbumen, and is present in the plasma in 

 the proportion of about 22 parts per thousand. It may be separated 

 from the remainder by filtering the plasma through magnesium sulphate, 

 which retains the metalbumen in a coagulated form and allows the 

 remaining liquid to pass through. The second substance, which has 

 passed through the filter, and which is coagulable by heat but not by 

 magnesium sulphate, is albumen proper. It has been called " serine" 

 by Denis and Robin, to indicate that it is the kind of albumen present 

 in blood-serum. It exists in the plasma in the proportion of about 53 

 parts per thousand, being accordingly rather more than twice as abun- 

 dant as the metalbumen. It is not known whether these two substances 

 are mutually convertible, or if so, which of them is produced by trans- 

 formation of the other. 



A certain quantity of albuminose is also to be found in the blood, 

 probably derived from the products of digestion. Its quantity, accord- 

 ing to Robin, varies from 1 to 4 parts per thousand. As it is absorbed 

 from the intestine during digestion, and neither accumulates in the 

 blood nor appears in any of the excretions, it is no cloubt transformed 

 into some other substance after being taken into the blood. 



