CHAPTER I. 



HEREDITARY TRANSMISSION OF MICROBIC DISEASES. 



THAT many of the infectious surgical diseases are hereditary 

 has been known for a long time, and many theories have been ad- 

 vanced at different times in the past in explanation of their occur- 

 rence. The modern views of this subject may be narrowed down 

 to two suppositions : 1. Transmission from parents to child of a 

 predisposition to certain diseases. 2. Transmission from parents 

 to fetus of the essential cause of the disease. The supposed heredi- 

 tary predisposition is interpreted as meaning anatomical or physio- 

 logical defects in the tissues, which render the organism susceptible 

 to the action of subsequent specific causes. The existence of 

 minute anatomical defects of bloodvessels, lymphatic glands and 

 vessels, connective-tissue spaces, etc., are looked upon as conditions 

 which favor localization of floating microbes, which find their way 

 into the body during post-natal life. An inherited defective vital 

 resistance on the part of the tissues to the action of pathogenic 

 bacteria is also considered by many in the light of an hereditary 

 influence in the causation of disease. The conditions are recog- 

 nized, but no satisfactory, demonstrative, or experimental proofs of 

 their existence have been furnished, and yet the immunity of some 

 animals to certain diseases cannot be explained in any other way 

 than in attributing to the tissues anatomical or physiological prop- 

 erties which protect the organism against the action of certain 

 microorganisms which, in other animals not so protected, produce 

 a fatal disease. Clinical experience has also shown that a great 

 difference is found among different persons in reference to suscepti- 

 bility to the same form of infection. In many persons, for in- 

 stance, inoculation with a pure culture of tubercle bacilli would be 

 a perfectly harmless procedure; in some it would produce a local, 

 latent tuberculosis; while in a few, rendered more susceptible to 

 this form of infection by antecedent hereditary or acquired causes, 

 the inoculation of the same number of bacilli would be followed 

 by rapid and extensive destruction of tissue, and death by early 

 and diffuse dissemination. The same can be said of nearly all, if 

 not all infectious diseases. If their existence has not been demon- 

 strated, we are, nevertheless, forced to recognize the influence of 

 certain as yet unknown conditions inherent in the tissues, and 



