90 THE BLOOD AND THE LYMPH 



slowly than normal animals. Regeneration is more rapid and complete 

 on a meat or mixed diet than it is during fasting. Regeneration is also 

 more rapid on a meat diet than on one of bread. Depletion of serum 

 proteins below 1 per cent is fatal. 



THE FERMENTS AND ANTIFERMENTS OF THE BLOOD 



The blood plasma contains many of the ferments present in the tissues. 

 The nature of these ferments has been the subject of many investiga- 

 tions in recent years, primarily because it has been found that they are 

 intimately connected with the problems of immunity. 



Among the ferments the following have been demonstrated in the 

 blood: 



Proteases are probably present normally in the human blood serum 

 in small amounts, but they are found in large amounts in the white 

 blood corpuscles. A protein foreign to the body if injected into the 

 blood ordinarily produces no untoward symptoms, but a second injec- 

 tion following the first by some days will produce symptoms of poison- 

 ing known as anaphylaxis. This fact has led to the assumption that 

 the injection of any foreign protein into the blood promptly leads to 

 the appearance therein of specific proteolytic enzymes which will digest 

 the strange protein into its derivatives, which are poisonous. This 

 power of the body to produce specific proteases has been the subject 

 of much research and debate, and Aberhalden proposed a test for preg- 

 nancy, for cancer, and for other conditions in which he made use of this 

 phenomenon. He believes that the presence of placenta or tumor tissue 

 causes proteins to be formed which bring about the production of specific 

 ferments whose duty it is to rid the system of these substances. Other 

 investigators fail to find the specificity in proteolytic action claimed by 

 Abderhalden, and believe that proteolytic ferments which are capable 

 of digesting foreign proteins are absorbed from the alimentary canal 

 from the digestive juices (Boldyreff ) . Some investigators fail to confirm 

 the claim that the proteolytic activity of the blood serum is increased under 

 the above conditions. 



Blood contains an antiferment known as antitrypsin. This can be 

 removed from the blood serum by several substances, among which are 

 kaolin, colloidal iron and starch. Serum thus treated shows strong pro- 

 teolytic activity and autodigestion will occur. In this case there can be 

 no question of the specific origin of proteases. Abderhalden believes 

 that the ferments of the blood of the pregnant woman are able to digest 

 the placental tissue. Human placental tissue has the ability of absorb- 

 ing antitrypsin and it is very questionable as to whether the test pro- 

 posed by Abderhalden is due to the new formation of ferments or to 



