31 



The following plan of handling rats has been found satisfactoiy 

 in the federal laboratory at San Francisco. The rats are nailed to a 

 shingle by an attendant. Another attendant reads off the address 

 on the tag attached to the rat, puts a check number on the shingle, 

 and records the address from which the rat was taken and the check 

 number on the card shown on page 48. This card is arranged so as 

 to give the data as to the address from which the rat came, its~size, 

 sex, and species. After being checked the rats are dissected and 

 finally, after examination by the medical officer, they are removed 

 from the shingle; any plague-infected rats are burned as soon as the 

 necessary investigation has been made. The dissection is made 

 by reflecting the skin from the whole front of the body and neck so 

 as to expose the cervical, axillary, and inguinal regions. The thoracic 

 and abdominal cavities are then opened with scissors. 



In the inspection, careful search for buboes must be made in the 

 regions of the various peripheral lymph glands. The abdominal and 

 thoracic organs must be subjected to a careful scrutiny. It is need- 

 less to say that this work should be done in a rat-proof, well-lighted 

 building that is provided with water, gas, and sewer connections. 

 The utmost care should be taken to avoid any undue risk of infection. 

 The wearing of rubber gloves is not necessary. Everyone who has 

 to handle infected animals must be sufficiently alive to the danger of 

 infection. 



In the extensive work conducted by the Indian Plague Commission 

 (3), attendants were protected with Haffkine's prophylactic. This is 

 undoubtedly a wise precaution and should be taken if possible. 



For a worktable on which to dissect the rats we use in San Francisco 

 a table which slopes gently from the sides and ends toward the center r 

 where a drain pipe is attached which leads to a vessel containing a 

 disinfectant. The table is covered with sheet lead. 



The layman of average intelligence readily leams to recognize the 

 gross lesions of rat plague and it is wise to train the laboratory at- 

 tendants to do this. Every rat should, however, be subjected to a 

 careful scrutiny by the physician responsible for the work. The great 

 majority of rats may be put aside after a cursory examination as en- 

 tirely beyond suspicion of infection. Probably 8 or 10 per cent of 

 them will require a very careful examination for the gross lesions of 

 plague. A card which we have found very useful for keeping records 

 of suspected and infected animals is shown on page 34. Probably all 

 of the species of the genus Mus are susceptible to plague infection. I 

 shall, however, confine myself to a consideration of plague in the rats 

 found the world over ( M. norvegicus, M. rattus, M. alexandrinus) . 



In Bombay (18) it has been found that the epizootic among Mus 

 norvegicus appears first and is probably responsible for the diffusion 

 of plague among Mus rattus. It precedes the infection among Mus 



