Asthma. Broken Wind. Heaves. Dyspna^a. 281 



cells, and smaller bronchial tubes. It may occur independently 

 of the vesicular emphysema but niore frequently, it is preceded 

 by that form and results from it. It is manifested on the surface 

 of the lung by irregularly formed tran.sparent elevations movable 

 from one place to another under the pressure of the finger con- 

 trary to what is the case in vesicular emphysema. These vary 

 from the size of a pea to that of a hen's Q^'g. When the air 

 exists in the cellular ti.ssne between the lobules it appears as in- 

 tersecting lines circuuLscribing irregular spans, and seemingly 

 dark colored to a superficial glance but seem to be transparent 

 on a closer examination. I^ike the elevations on the surface these 

 collapse on being pricked. 



When a lung in this state has been inflated and dried it presents 

 on the diseased parts the union of several air .sacs into one by the 

 rupture of their intervening walls so that a pea may be lodged in 

 the cavit}^ ; it further shows wide and prolonged canals on the 

 surface and in the intervals between the lobules — the dilated 

 areolae of the connective tissue. These abnormal conditions like 

 the vesicular emphysema are chieflj^ met within the anterior lobes 

 of the lungs along their free borders and on their inner surface 

 near the entrance of the bronchi. 



One or both of these two forms of emphysema may be con- 

 sidered as essential conditions in all forms of broken wind. It 

 does not follow that this is the primary disease ; we have already 

 seen that the cause of the malady is usually to be sought on the 

 side of the digestive organs, and that impaired innervation, on 

 the part of the vagus nerve or of the ganglia in the brain presid- 

 ing over it, leads to these functional and structural changes in 

 the lungs. If these changes are results and not causes, their ex- 

 tent will not necessarily bear a constant proportion to the intensity 

 of the disease, though in reality they are generally found to do so. 



From a series of injections of lungs from broken-winded horses 

 M. Demoussy arrived at the conclu.sion that the essential lesion 

 of broken-wind was an aneurismal dilatation of the capillary ves- 

 sels of the lung. This is like the condition of the mucosa found 

 in asthma in man and is explainable in both cases by the impaired 

 innervation, as dilatation of these minute vessels is a natural con- 

 sequence of the loss of vaso-motor nervous power, and contact 

 with air saturated with carbonic acid. 



