INFECTION AND IMMUNITY I 6 2 a 



and the enzyme of the macrophages resembling 

 pepsin in its action. The blood serum, on the 

 other hand, contains an antienzyme. The varying 

 relation existing between these enzymes and the 

 antienzymes serves to explain how the same irritant 

 in the same quantity may cause two different types 

 of inflammation. This is well illustrated by the 

 following experiment made by Opie: 1 If a small 

 quantity of turpentine is injected into the sub- 

 cutaneous tissue of dog, a large fluctuating abscess 

 filled with creamy pus is formed within four days; 

 there is a widespread undermining of the skin. 

 The same quantity of turpentine injected into the 

 pleural cavity causes a serofibrinous inflammation 

 which undergoes resolution so that the pleural 

 cavity is restored to its normal condition after about 

 ten days; there is no destruction of tissue and a 

 scar is not formed. In the subcutaneous tissue 

 only a small amount of oedematous exudate can 

 accumulate; the undiluted irritant causes active 

 migration of leucocytes so that the antibody of the 

 exuded serum is soon overbalanced by the enzyme 

 set free by disintegrated pus cells. In the pleural 

 cavity, on the contrary, a large quantity of serum 

 quickly accumulates and the exudate is sero- 

 fibrinous instead of purulent; the antienzyme it 

 contains is capable of holding in check the enzyme 



1 E. L. Opie, Lecture before the Harvey Society, New York, 

 Feb. 1910. The Harvey Lectures, J. B. Lippincott Co. 1910. 



