324 DISEASES OF CATTLE, SHEEP, GOATS, ETC. 



flakes. If mucus is present at the same time, the bile may become so 

 viscid that when it is poured from one glass to another it forms long 

 bands. The bile in health is a limpid fluid containing no solid 

 particles. 



If the animal has not been observed during life to pass urine 

 colored with blood or red water, the bladder should be opened. This 

 quite invariably, in acute cases, contains urine which varies in color 

 from a deep port wine to a light claret. In many cases the color is so 

 dense that light will not pass through even a tnin layer. The kid- 

 neys are always found congested in the acute attack. The disease 

 exerts but little effect on the stomach and intestines beyond more 

 or less reddening of the mucous membrane; hence an examination 

 of these may be safely omitted. The lungs are, as a rule, not dis- 

 eased. The heart usually shows patches of blood extravasation on 

 the inside (left ventricle), and less markedly on the outer surface. 



We have observed jaundice of the various tissues but very rarely. 

 It has been observed by some quite regularly, however. 



During the hot season about 90 per cent of the susceptible ma- 

 ture animals from a noninfected district die, but later, in the cool 

 weather, the disease assumes a milder type, with a consequent de- 

 crease in the number of deaths. 



The Cattle Tick, Margaropus Annulatus, as the Carrier of Texas 

 Fever. The cattle tick is, as its name indicates, a parasite of cattle 

 in the southern part of the United States. It belongs to the group of 

 Arthropoda and to the genus Margaropus (Boophilus), which is 

 included in the order Aearina. Its life history is quite simple and 

 easily traced from one generation to another. It is essentially a par- 

 asite, attaching itself to the skin and drawing the blood of its host. 

 It is unable to come to maturity and reproduce its kind unless it be- 

 comes attached to the skin of cattle, whence it may obtain its food. 



The eggs laid on the ground after the female has dropped from 

 the host begin to develop at once. When the embryo is fully formed 

 within the shell it ruptures this and gains its freedom. The time 

 required from the laying of the eggs to their hatching varies consid- 

 erably, according to the temperature. In the laboratory in the heat 

 of midsummer this was accomplished in about thirteen days. In the 

 late fall, under the same conditions, it required from four to six 

 weeks. The larva after emerging from the egg is very minute, six- 

 legged, and just visible to the naked eye. If these larvae be kept on 

 a layer of moist sand or earth in a covered dish, they may remain 

 alive for months, but there is no appreciable increase in size. As 

 soon, however, as they are placed upon cattle growth begins. 



On pastures these little -creatures soon find their way onto cat- 

 tle. They attach themselves by preference to the tender skin on the 

 escutcheon, the inside of the thighs, and on the base^of the udder. 

 Yet when they are very numerous they may be found in small num. 

 bers on the various parts of the body, such as the neck, the chest, and 

 the ears. 



The changes which they undergo during their parasitic exist- 

 ence were first studied by Dr. Cooper Curtice in 1889. The young 



