502 DEFENSES AGAINST DISEASE 



or precipitate foreign proteins out of the blood. They are used 

 as a test for specific bloods, human and other animals. 



Opsonins prepare the germs for ingestion by the white corpuscles. 

 Opsonins seem to combine in some way with the bacteria and so 

 alter them that the white corpuscles can better engulf them. 

 There are different opsonins produced by the blood in combating 

 tuberculosis, boils caused by a staphylococcus, and meningitis. 

 When opsonins are present, the white corpuscles are better able 

 to destroy the bacteria. The test for the amount of opsonins 

 in a patient's blood is a very interesting one. For example, blood 

 is taken from a patient suffering from tuberculosis, and the serum 

 is separated from it. The amount of opsonins in this serum is to 

 be measured. The serum is mixed with white corpuscles from a 

 healthy animal or person. The white corpuscles are well washed 

 to make sure that no opsonins are in the mixture before the 

 serum is added. The serum and white corpuscles are then 

 added to some tuberculosis bacilli. A little of this mixture is 

 put on a glass slide, stained, and examined under the microscope. 

 Then a count is taken, either of the number of bacteria ingested 

 by the first hundred corpuscles seen, or an estimate of the per 

 cent of the first hundred white corpuscles seen to have ingested 

 bacteria. The second estimate is easier than the first because 

 the white corpuscles devour so many bacteria that in some cases 

 it is impossible to count them. The estimate is then compared 

 to normal blood in order to see the increase of opsonins present, 

 and thus determine the increase in the activity of the white cor- 

 puscles. Any difference in the white corpuscle activity is attrib- 

 uted to extra opsonins developed in the patient's blood. 



The relation of mental poise to disease. In his farewell address 

 as the retiring dean of the college of physicians and surgeons of 

 one of the large universities, a famous doctor stated that the sugar 

 pill was the outstanding discovery of his generation. He stated 

 in very decided terms that his long years of experience had con- 



