COMMUNICABLE DISEASES 397 



In some diseases the mortality rate is very high, as in yellow fever, 

 beri-beri, tetanus, cholera, plague and leprosy. In others it is low, as in 

 syphilis, gonorrhea, malaria, whooping cough, mumps and varicella. In 

 certain diseases the prognosis is rather uncertain, the mortality rate being 

 high at times and again low, as in scarlatina, small-pox, measles and grippe. 

 In the recent grippe or influenza pandemic the mortality rate was unus- 

 ually high. In this disease the mortality rate is high at the early periods 

 of the invasion, gradually growing less and less severe. It may be that 

 the causative organism, whatever it may be, loses in virulency in its 

 passage through the hosts. The hemorrhagic form of smallpox has a 

 mortality rate of nearly 100 per cent, whereas some epidemic forms of 

 this disease are very mild, showing practically 100 per cent, recoveries. 

 The so called black scarlatina shows a very high mortality rate. Some 

 epidemics of measles show a comparatively high mortality rate. Some 

 diseases run a somewhat variably rapid course as pneumonia, diphtheria, 

 spinal meningitis, bubonic plague and Asiatic cholera, ending either 

 in death or recovery. Other diseases, as scarlet fever, measles and 

 diphtheria may have after-effects or sequelae which often assume a chronic 

 course and may finally result in death. Certain diseases run a regular 

 course which varies but little as to the sequence of symptoms and duration, 

 as typhoid fever (five weeks). Others run a variably chronic course, 

 ending either in death or recovery, as pellagra and malaria. Some diseases 

 are very persistent, difficult to eradicate from the system, showing certain 

 effects even to the third and fourth generations, as tuberculosis and syphilis 

 Malaria leaves certain after-effects, as enlarged spleen ("ague cake")> 

 which may persist through life. 



Savage races are peculiarly susceptible to certain diseases, as tubercu- 

 losis, small-pox, gonorrhea and syphilis and peculiarly enough these 

 diseases did not originate with primitive peoples, but with advanced 

 civilization, though of great antiquity. 



DISSEMINATION OF DISEASE 



The manner in which disease is spread has been indicated in the pre- 

 cedeing but the subject has not been fully discussed. The student of 

 pharmacy should have a course in general sanitary science and in pre- 

 ventive medicine. The general principles of immunity have been dis- 

 cussed and the more important communicable diseases have been briefly 

 outlined, but the vast subject of preventive medicine has not been touched 

 upon. This must be taken up in a separate course. 



The agents and agencies concerned in the spreading of communicable 

 diseases and others, constitute the groundwork of preventive medicine. 



