1346 SPOTTED FEVER OF THE ROCKY MOUNTAINS 



liver and spleen are enlarged, congested, and soft, and the kidneys 

 are congested, and may show subcapsular haemorrhages. 



Histo-pathology. — ^The microscope shows capillary congestion of 

 the organs, with an excess of leucocytes, and an extravasation into 

 and pigmentation of the skin. Acute parenchymatous degenera- 

 tions of the heart muscle, the sp''een, liver, and kidneys, are also to 

 be noted. 



Symptomatology — Incubation. — ^The incubation period varies from 

 two to seven days, during which prodromata, in the form of irritation 

 in the tick-bites, from which pains may radiate, and chilliness with 

 malaise and nausea, may be experienced. 



Onset. — ^The illness often begins with a distinct chill, accompanied 

 by severe headache, pains in the back and other parts of the body, 

 and a rapid rise of temperature to 103° to 104° F., associated with 

 a furred tongue, a dry skin, yellow and congested conjunctivae, an 

 irritating cough, at times epistaxis, and the passage of febrile 

 urine. 



The fever continues to rise, with slight morning remissions, 

 until a maximum of 105° to 107° F. is reached about the fifth to 

 the twelfth day. About the third day (second to seventh) a 

 macular eruption appears on the wrists and ankles which quickly 

 spreads up the arms and legs on to the back, forehead, chest, and 

 abdomen, so that the whole body is included in about one to two 

 days. The macules vary in size from i to 5 millimetres in diameter. 

 They are not elevated, and at first disappear on pressure, but 

 liter become permanent, and finalty turn petechial about the sixth 

 to the tenth day. Associated with the eruption is a dusky-red 

 mottling of the skin, and often a subicteric tinge of both the skin 

 and the conjunctivae. The eruption is, however, by no means 

 always well marked, and, in fact, mild cases have been reported 

 in which it was absent. 



The pulse is from the first very rapid, reaching from 110 to 150 

 per minute, and not as a rule in proportion to the temperature. 

 At first full and strong, it becomes gradually feebler and smaller, 

 and is often dicrotic, and in severe cases may be intermittent and 

 irregular. The blood shows a diminution of the erythrocytes and 

 haemoglobin, with a slight increase in the total number of leuco- 

 cytes and a relative increase of the mononuclear leucocytes; but 

 in considering these blood-counts, allowance must be made for the 

 altitude at which the disease occurs. (Edema of the face and 

 limbs may be present in severe cases. 



Course. — ^At first the tongue is covered by a thick white fur, but 

 later it becomes dry, cracked, and brownish, and sordes collect on the 

 teeth. Nausea may be present during the first week, but is more 

 common in the second, and generally lasts till the end of the illness. 

 Constipation is usually present throughout the attack, and the 

 liver is often slightly enlarged, while the spleen extends beyond the 

 costal margin, and is tender. There is usually a slight sore throat, 

 and there may be signs of a mild bronchitis, associated with an 



