588 DISEASES OF THE ARTERIES AND LYMPHATICS. 



patclies of a yellowish colour will be found scattered on its 

 inner surface, wliilst deposits of earthy matter alternate with 

 the fat. 



I have seen gangrene of the tail in cows, particularly old cows. 

 May it not have been due to this condition of the arterial coats ? 

 The subject is well worthy of further consideration. 



INJURIES TO ARTERIES. 



Tn the lower animals wounds of arteries are fortunately rare. 

 When an artery is wounded the haemorrhage is much more rapid 

 than from a vein ; the blood is of a bright red colour, and dis- 

 charged in jets, synchronous with the contraction of the heart. 

 At first the stream is full, and is pushed from the wound with 

 considerable force ; but as the animal grows faint the jerks are 

 more perceptible, and the flow diminishes. Wlien an artery is 

 torn it is unequally lacerated ; its external coat is twisted and 

 drawn out, whilst the divided internal and middle ones retract, 

 and are thrown towards the centre of the canal. The elasticity 

 and vitality of all the coats are impaired for some little distance 

 from the wound, and the current of blood in the injured part is 

 diminished or altogether arrested for some distance, and the 

 bleeding is thus prevented. 



If an artery be split in a longitudinal direction and across the 

 course of the circular fibres, the bleeding is most profuse when 

 the part is relaxed ; but if it be kept on the stretch, the bleed- 

 ing becomes less profuse. If an artery has been cut partially in 

 a transverse direction the bleeding is very profuse, for the trans- 

 verse fibres separate from each other, and the opening gapes. 

 Cutting an artery completely across is attended with its retrac- 

 tion within the sheath and surrounding tissue, and the bleeding 

 is arrested if the vessel is not large. Thus, when the palatine 

 artery has been partially divided, the haemorrhage continues ; 

 but if the incision be made deeper, and the artery completely 

 cut across, the bleeding gradually ceases. 



In the case of a large artery, however, this proceeding is not 

 sufficient, although the bleeding may be arrested as the animal 

 grows faint, the pressure of the surrounding clot being sufficient 

 at the time to arrest the bleeding ; but no sooner does the faint- 

 ness pass away, and the circulation become strong again (unless 



