25 



thus 0-5 c.c. of the 1 in 50 dilution contains a dose of 0-01 c.c of broth 

 culture. 



Injection. — The serum, as well as the culture, is administered by means 

 of a glass tube graduated to deliver 0-5 c.c, one end of which is drawn 

 out to take the needle. A firm union is made between glass and needle 

 by means of a piece of rubber valve tubing on which the mount of the 

 needle fits. Delivery is controlled by the mouth through a long piece of 

 rubber tubing which fits over the wool plugged end of the glass tubing. 



P. M. Examination. — After the death of a mouse the blood is examined 

 microscopically to confirm the existence of pneumococcus septicaemia, 

 and if there is any doubt as to the cause of death, plate cultures are made 

 from the blood. 



The chief difficulty in the performance of protection tests is 

 the maintenance of test cultures of standard virulence. Many 

 of the strains of Group IV could not be used for protection 

 tests, &< it was impossible to increase the virulence up to the 

 necessary degree. Protection experiments with strains of inter- 

 mediate or irregular virulence may give misleading results. 

 To bring the test culture up to maximum virulence it was in- 

 variably passed through a mouse the day before the test and the 

 culture from the heart's blood served as the test culture. 



Uniformity of Technique for the Diagnosis of Type. 



The study of the serological types of pneumococci has made 

 definite progress during the last few years and one may consider 

 whether the time has now arrived when the adoption of uniformity 

 of diagnostic methods may safely be recommended. The ad- 

 vantages of a uniform technique for the comparison of the results 

 of different workers are obvious, but premature standardisation 

 would lead to the stereotyping of a procedure which had not passed 

 the test of prolonged general trial. This disadvantage might 

 be obviated if each observer would control the results of the 

 standard test by his own method and would publish any dis- 

 crepancy between the two. The apparent divergencies, for 

 example, between the results of the Pasteur and Rockefeller 

 Institutes* can only be cleared up by the adoption of uniformity 

 in technique and comparison of methods as advocated above. 

 Until then it will be impossible either to obtain exact informa- 

 tion upon the distribution of the three fixed types in different 

 countries, or to make progress towards a useful classification 

 of the so-called atypical strains of pneumococci which are found 

 less commonly than the fixed types in cases of lobar pneumonia. 



I therefore make, for the consideration of other workers in this 

 field, the following suggestions towards the formulation of a 

 uniform diagnostic test. In the first place a standard technique 

 should be based on the methods of the Rockefeller Institute, 

 the results of which have been confirmed in many countries ; 



* A sample of the Pasteur Institute Type II serum (horse) which 

 Dr. Truche kindly sent me agglutinated the Rockefeller Type I in my 

 possession but not the Type II. Protection by the above serum was 

 conferred on mice against both types, but more strongly against Type I 

 than against Type II. 



