MECHANISM OF PROTEIN HYDROLYSIS AND IMMUNIZATION 27 



sion, hydrolyze nitrogenous molecules of the polypeptid order, 

 and give out antitoxic ferments in response to specific toxins. 

 But as a rule the tissues are shielded by the red blood corpuscles 

 from the necessity of performing these functions. 



5. The vast multitudes of red blood corpuscles, with an aggre- 

 gate bulk of about four pounds in the ordinary human body, 

 their substance having been synthesized by the mother cells out 

 of amino-acids, constitute the chief source of the specific pro- 

 teins in the blood stream, which proteins on being decompounded 

 (possibly with the aid of the lymphocytes and polynuclears) are 

 the prominent sources of bodily energy. 



6. Every cell that can unite with a foreign proteid product 

 can produce an "antibody" calculated to antagonize that prod- 

 uct. The leucocytes and red blood corpuscles are the particular 

 cells that come most in contact with such foreign bodies, and 

 they are therefore the chief source of specific proteolytes and 

 antibodies directed against the invaders. The presence in the 

 blood stream of these specific proteolytes and antibodies, se- 

 creted by the leucocyte and red cells, and to a certain extent by 

 the body-cells (backed up by the presence of an adequate army 

 of leucocytes and red cells themselves, capable of producing more 

 of the antibodies under stimulus of invasion), constitutes the 

 condition of immunity. 



7. Immunization to bacterial disease is merely a special case 

 of protein assimilation. It has in the past been as necessary 

 to acquire immunization against the dietetic proteins oyster, 

 fish, egg, fowl, milk, mutton, pork, beef and against "benign" 

 bacteria as against the most virulent bacteria. 



8. So-called harmless or benign bacteria are those that have 

 been long with us, and which, therefore, the leucocytic and ery- 

 throcytic mechanisms have learned adequately to combat and con- 

 trol. Virulent bacteria are the relatively rare ones or those that 

 have visited us infrequently. A relatively benign bacterium may 

 become malignant, however, through changed conditions leading 

 it to ingest unwonted types of protein ; or through developing 

 exceptional vigor; or through invading the system in excessive 

 numbers. 



9. Protein anaphylaxis of any type (including "serum disease") 

 is merely a special case of protein intoxication, strictly homolo- 

 gous with protein poisoning from the toxins of virulent bacteria. 

 It results when a general proteolytic (leucocytic) enzyme is pres- 

 ent in sufficient quantity to hydrolyze the foreign protein partly, 

 while the red-cell mechanism is temporarily exhausted, so that 

 cleavage cannot be completed, and the tissue cells in particular 

 the brain cells are attacked. Protein anaphylaxis is strictly 

 homologous with protein immunization. They are different as- 



