OF VETERINARY MEDICINE. 65 



and this produces pressure on the gastric periphery of the pneu- 

 mogastric nerves. This is the starting point of heaves. It 

 starts in the stomach. This pressure effects these peripheral 

 nerves, increases their irritabiHty. This disturbed condition of 

 the nerves constitutes what is known as neurosis. The neural 

 disturbance works upwards and forwards through the pneu- 

 mogastric and involves the pulmonary and more or less the 

 cardiac branches. The pulmonary branch is lessened in tonicity 

 which allows the vesicles to dilate by reducing their tonicity. 

 These vesicles dilate a little more and more every day until 

 finally the dilatation becomes chronic. 



In connection with the pathogenesis, especially as it refers to 

 morbid anatomy, notice the results on the vesicle walls. The 

 first affect of the dilatation is anaemia of the vesicle walls. This 

 is- a natural mechanical result. The second eft"ect is irritation, 

 and then follows a mild subacute inflammation which runs into 

 a chronic. The only evidence we have of chronic inflammation 

 in these air vesicles is cell proliferation. This produces a thick- 

 ening of the walls of the vesicles and destroys their contractility. 

 If the early development of the disease is rapid you may get 

 rupture of several vesicles into one large one. Imagine that this 

 is quite general throughout the lungs and you can imagine you 

 are going to have considerable disturbance in respiration. In 

 this pathogenic connection you will 'find that the horse is worse 

 at times; this is due to the condition of the stomach. If a 

 heavy horse gets an unusually big load of food in the stomach 

 you will have increased irritability of the pneumogastric nerves 

 and the pulmonary branches as well. This irritability of the 

 sympathetic system that supplies the unstripped muscular fibres 

 prod'Tces spasms of them. 



Symptoms. — Heaves may be incipient or confirmed. In in- 

 cipient heaves you have the disturbed function without the mor- 

 bid anatomy. In confirmed heaves you have the disturbed func- 

 tion and morbid anatomy. It is therefore difficult in some cases 

 to diagnose a case of incipient heaves. If the doctor can diag- 

 nose this he can cure it. Anybody can diagnose confirmed 

 heaves, but nobody can cure it. 



The symptoms of incipient heaves are as follows: Breathmg 



