022 SPORADIC DISEASES. 



the dilated portions. If there be any part of the lung that will 

 not dilate, then other parts are over-dilated to fill up tlie 

 vacuum, and in that way those parts which we distend are over- 

 distended, in order to compensate for the want of distension in 

 other parts ; and when once of^r-distended they are often 

 unable to recover themselves, just as is the case in other parts 

 of the body — the urinary bladder for example. 



2. Interlobular Emphijsema, or accumulation of air or gases in 

 the meshes of the connective lung tissue, may arise from rup- 

 ture of the walls of the air vesicles. Thiss result of rupture is, 

 however, an uncommon occurrence, for generally, when the cells 

 are ruptured, they break one into another, and form permanent 

 enlargements, with rigid walls, by coalescence ; but acute emphy- 

 sema is, however, seen in various diseases, especially of horned 

 cattle, from rupture of air cells or ho\\\ the evolution of gases, 

 which infiltrate and distend the pulmonary areolar tissue. It 

 may be induced artificially by the injection of the bicarbonate of 

 soda into the veins. It is also seen in an animal which has 

 been destroyed by " blowing," i.e., by forcing air into the 

 jugulars. 



Snarry, of York, in a private letter to me, records several 

 cases of subcutaneous emphysema in cattle, the syn)ptoms of 

 which were as follows : — 



, The breathing is short, catchy, the air expelled by a double 

 effort, and often associated with a grunting or moaning expira- 

 tory sound. In most cases the head is drooping, eyes dull, 

 and the ears flaccid ; whilst in others the animal manifests 

 great anxiety, and even some amount of dread or terror, as if 

 each respiratory movement were a source of pain, and possibly 

 there is actual pain, caused by the tissues being dissected by 

 each ingress of air ; indeed it may be said that when the patient 

 has completed one respiratory movement its seems to dread the 

 pain of the next. There is always some stiffness of gait, particu- 

 larly when turned round, and in many instances a subcutaneous 

 emphysematous swelling makes its appearance, sometimes on 

 the first day, but more frequently on the second, third, or fourth 

 day, or even later, after the manifestation of illness. This 

 emphysematous swelling may be first noticed on one or both 

 sides of the chest, the loins — one or both loins ; but it gradually, 

 sometimes quickly, extends from its original seat to neck, head. 



