DISEASES OF CATTLE 21 



in man, owing to the greater bulk of tissue surrounding them and 

 the pectorial position of the fore extremeties, all of which render it 

 more difficult in determining pathological conditions. 



The air going in and out of the lungs makes a certain soft, 

 rustling sound, known as the vesicular murmur, which can be heard 

 distinctly in a healthy state of the animal, especially upon inspira- 

 tion. Exercise accelerates the rate of respiration and intensifies this 

 sound. The vesicular murmur is only heard where the lung con- 

 tains air and its function is active. The vesicular murmur is weak- 

 ened as inflammatory infiltration takes place and when the lungs 

 are compressed by fluids in the thoracic cavity, and disappears when 

 the lung becomes solidified in pneumonia or the chest cavity filled 

 with fluid as in hydrothorax. The bronchial murmur is a harsh, 

 blowing sound, heard in normal conditions by applying the ear over 

 the lower part of the trachea, and may be heard to a limited extent 

 in the anterior portions of the lungs after severe exercise. The 

 bronchial murmur when heard over other portions of the lungs gen- 

 erally signifies that the lung tissue has become more or less solidi- 

 fied or the fluid has collected in the chest cavity. 



Other sounds, known as mucous rales, are heard in the lungs 

 in pneumonia after the solidified parts begin to break down at the 

 end of the disease and in bronchitis where there is an excess of se- 

 cretion as well as in other conditions. Mucous rales are of a gur- 

 gling or bubbling nature. They are caused by air rushing through 

 tubes containing secretions or pus. They are said to be large or 

 small as they are distinct or indistinct, depending upon the quan- 

 tity of fluid that is present and the size of the tubes in which the 

 sound is produced. According to their character they are divided 

 into dry and moist. The friction sound is produced by the rubbing 

 together of roughened surfaces and is characteristic of pleurisy. 



Percussion. Percussion is that mode of examination by which 

 we elicit sounds by striking or tapping over the part. It may be 

 direct or indirect. If the middle finger of the left hand is placed 

 firmly on the chest and smartly tapped or struck with the ends of 

 the first three fingers of the right hand, the sound will be noticed to 

 be more resonant and clear than when the same procedure is prac- 

 ticed on a solid part of the body. This is because the lungs are not 

 solid, but are always, in health, well expanded with air. But in 

 certain pulmonary diseases, as in pneumonia, they fill up and be- 

 come solid, when the sound given out by percussing them is dull, 

 like that on any other solid part of the animal. When fluid has 

 collected in the lower part of the chest cavity the sound will also 

 be dull on percussion. Where there is an excess of air in the chest 

 cavity, as in emphysema or in pneumothorax, the percussion sound 

 becomes abnormally loud and clear. By practice on healthy ani- 

 mals the character and boundaries of the sounds can be so well de- 

 termined that any variations from them will be readily detected, 

 and will sometimes ^disclose the presence of a diseased condition 

 when nothing else will. 



