6 
The exact sequence as g-iven on the following pages is not strictly 
adhered to, because it is the desire of the director to make the course 
as practical as circumstances will permit. Therefore, the study of 
diphtheria is usually left until the fall of the year or winter, when 
practical experience may be had with the cases which usually occur in 
the District. The studies upon vaccinia and smallpox are taken up 
during the winter months, which time is more apt to oder material 
and cases. Malarial work is of course largely conlined to the summer 
and fall seasons. 
In connection with the health department of the District, the work 
of diagnosing diphtheria from swabs and culture tubes and the admin- 
istration of antitoxin, both for prophylactic and curative purposes, is 
carried on by each student-officer. In connection with the studies 
upon vaccinia, a visit is always made to one of the large vaccine farms, 
which offers special advantages for observing the process of vaccinat- 
ing- the calves, obtaining the lymph and pulp, glycerinating the virus, 
and preparing the product for market. In like manner advantage is 
taken, so far as it is practicable, of the material in hospitals and other 
institutions situated in the District of Columbia. 
It will be noticed that in this edition more attention is given to the 
subjects of pathologic histology, and a short review in normal histology 
has also been added. A collection of tumors and pathologic processes 
has been obtained fi’om various sources and these are cut. stained, 
mounted, and studied by each student- officer; and these specimens are 
used to demonstrate the quiz which is conducted by the director of the 
Ir.boratory. The pathologic histology of all infectious processes upon 
the lower animals, which are studied in the laboratorv. are thoroughlv 
worked up by each student-officer in a systematic manner. Tumors 
and other specimens are received from time to time from the various 
hospitals and quarantine stations of the Service, and similar advantage 
is taken of such material. 
In view of the growing importance of animal parasites in the causa- 
tion of disease, a Division of Zoologw has been added to the Hvgienic 
Laboratorv and the chief of this division gives each student-officer 
instruction in the various organisms of this class parasitic to man. 
It will also be noticed that considerable importance is given to the 
subject of disinfection and disinfectants. This arises from the fact 
that officers of the Service are required not only in their hospital work, 
but more especially in their quarantine and public health duties, to 
thoroughly understand the theory and practice of this important sub- 
ject. Each student-officer is required to master the theory and mechan- 
ics of all the important disinfecting apparatus and to make actual tests 
upon the efficiency and value of each one. 
The scientitic workers in the laboratorv meet one evening each week 
in order to review the work of the week and to discuss the current 
