CLINICAL OBSERVATIONS. 183 



SEX, AGE, AND INCUBATION PERIOD. 



Both sexes seem equally susceptible, but the proportion of 

 females and children attacked during the epidemic was compar- 

 atively small, as women and children were evidently not so 

 frequently exposed to infection. The disease prevailed partic- 

 ularly among the poorer classes, coolies, etc., the majority of 

 whom were between 20 and 40 years of age. The incubation 

 period varied from two to five days, though usually it was not 

 over two or three days. 



SYMPTOMS. 



The following summary of the clinical features of the disease 

 has been made largely from personal observations during the 

 epidemic in Mukden and also from evidence presented at the 

 International Plague Conference. 



The onset of the disease is usually somewhat abrupt; prod- 

 romal symptoms are rare. The disease usually begins with 

 chilly sensations, but a distinct rigor generally does not occur. 

 Epistaxis is generally not present. There is headache, loss of 

 appetite, an increase in the pulse rate, and fever. Vomiting 

 rarely occurs. Within from twenty-four to thirty-six hours after 

 the onset, the temperature usually has reached 103° or 104° F., 

 and the pulse 110 to 130 or more beats per minute. Cough and 

 dyspnoea usually appear within twenty-four hours after the 

 onset of the first symptoms. The cough is usually not painful. 

 The expectoration is at first scanty, but soon becomes more 

 abundant. The sputum at first consists of mucus which shortly 

 becomes blood-tinged. Later the sputum becomes much thinner 

 and of a bright-red color ; it then contains enormous numbers of 

 plague bacilli in almost pure culture. The typical rusty sputum 

 of croupous pneumonia has not been observed. The conjunctivae 

 become injected, and the tongue coated with either a white or 

 bro\Miish layer. The expression is usually anxious, and the face 

 frequently assumes a dusky hue. Labial herpes has never been 

 observed. The patients sometimes complain of pain in the chest, 

 but usually this is not severe. Apart from the disturbances due 

 to the dyspnoea and their anxiety for their condition, they usually 

 appear to suff"er but little and usually do not complain of pain. 

 In the later stages of the disease, the respirations become greatly 

 increased and the dyspnoea usually very marked, the patients 

 frequently gasping for air for several hours before death. Cya- 

 nosis is then common. 



The signs of cardiac involvement are always marked in the 



