TRANSACTIONS OF SECTION I. 779 



sheep is called the immune body; the ferment-like substance destroyed by heat is 

 the complement. The latter is not specific, since it is furnished by the blood of 

 non-immunised animals, but it is nevertheless essential for haemolysis. Ehrlich 

 believes that the immune body has two side groups — one which connects 

 ■with the receptor of the red corpuscles and one which unites with the hapto- 

 phor group of the complement, and thus renders possible the ferment-like action 

 of the complement on the red corpuscles. Various antibacterial serums which 

 have not been the success in treating disease they were expected to be are probably 

 too poor in complement, though they may contain plenty of the immune body. 



Quite distinct from the bactericidal, globulicidal, and antitoxic properties of 

 blood is its agglutinating action. This is another result of infection with 

 many kinds of bacteria or their toxins. The blood acquires the property of 

 rendering immobile and clumping together the specific bacteria used in the infec- 

 tion. The test applied to the blood in cases of typhoid fever, and generally called 

 "Widal's reaction, depends on this fact. 



The substances that produce this effect are called agglutinins. They also are 

 probably proteid-like in nature, but are more resistent to heat than the lysins. 

 Prolonged heating to over 60° C. is necessary to destroy their activity. 



^'Lastly, we come to a question which more directly appeals to the physiologist 

 than the preceding, because experiments in relation to immunity have furnished 

 us with what has hitherto been lacking, a means of distinguishing human blood 

 from the blood of other animals. 



The discovery was made by Tchistovitch (1899), and his original experiment 

 •was as follows :— Rabbits, dogs, goats, and guinea-pigs were inoculated with eel- 

 serum, which is toxic: he thereby obtained from these animals an antitoxic serum. 

 But the serum was not only antitoxic, but produced a precipitate when added to eel- 

 serum, but not when added to the serum of any other animal. In other words, not 

 only has a specific antitoxin been produced, but also a specific precipitin. Numerous 

 observers have since found that this is a general rule throughout the animal king- 

 dom, including man. If, for instance, a rabbit is treated with human blood, the 

 serum ultimately obtained from the rabbit contains a specific precipitin for human 

 blood ; that is to say, a precipitate is formed on adding such a rabbit's serum to 

 human blood, but not when added to the blood of any other animal.' The great 

 value of the test is its delicacy : it will detect the specific blood when it is greatly 

 diluted, after it has been dried for weeks, or even when it is mixed with the 

 blood of other animals. 



I have entered into this subject at some length because it so admirably illus- 

 trates the kind of research which is now in progress ; it is also of interest to others 

 than mere physiologists. I have not by any means exhausted the subject, but for 

 fear I may exhaust my audience let me hasten to a conclusion. I began by 

 eulogising the progress of the branch of science on which I have elected to speak 

 to you. Let me conclude with a word of warning on the danger of over- 

 ifpecialisation. The ultra-specialist is apt to become narrow, to confine 

 himself so closely to his own groove that he forgets to notice what is occurring 

 in the parallel and intercrossing grooves of others. But those who devote them- 

 selves to the chemical side of physiologj- run but little danger of this evil. The 

 subject cannot be studied apart from other branches of physiology, so closely are 

 both branches and roots intertwined. A s an illustration of this may I be permitted 

 to speak of some of my own work ? During the past few years' the energies of 

 my laboratory have been devoted to investigations on the chemical side of 

 nervous activity, and I have had the advantage of co-operating to this end with 

 a number of investigators, of whom 1 may particularly mention Dr. Mott and 

 Dr. T. G. Brodie. But we soon found that any narrow investigation of the chemical 

 properties of nervous matter and the changes this undergoes during life and after 

 death was impossible. Our work extended in a pathological direction so as to 

 investigate the matter in the brains of those suff'ering from nervous disease ; it 



' There may be a slight reaction with the blood of allied animals ; for instance, 

 with monke3''s blood in the case of man. 



