INVERSION OF THE BLADDER 371 



of small laminated calculi, aggregated together and enclosed in an amor- 

 phous deposit. 



All vesical calculi do not originate in the bladder. Some no doubt 

 have their beginning in the pelvis of the kidney, in which position we 

 have repeatedly found them in their rudimentary condition. Many of 

 these renal formations, on reaching the bladder, are ejected with the 

 urine, but occasionally such as acquire large dimensions are retained in 

 the vesical cavity and undergo enlargement by earthy incrustation. 



It is certain, however, that stone formation is not always the direct 

 outcome of the conditions indicated above. Foreign substances, we are 

 aware, sometimes find their way into the bladder of the horse, notwith- 

 standing the seeming difficulty of such an event. Some years ago Mr. 

 William Hunting, of London, brought to the notice of the Central 

 Veterinary Medical Society such a case, where a piece of stick, some four 

 or five inches in length, and as thick as the little finger, was found stretch- 

 ing across the bladder of a horse, with one end projecting through its 

 walls into the pelvic cavity. It had evidently occupied this position 

 some considerable time, as a large calculus had formed around its central 

 portion. Whence the stick had come there was no direct evidence to 

 show, and we are left to assume its possible introduction through the 

 abdominal walls or through the alimentary canal. Such an accident as 

 that first referred to is quite possible, but for many considerations does 

 not recommend itself to our acceptance. From facts which have recently 

 come to light in the human subject, we are more disposed to accept the 

 explanation Avhich refers its entrance into the bladder through the medium 

 of the alimentary canal. 



INVEESION OF THE BLADDER 



The bladder of the mare may be turned inside out by spasmodic 

 contraction of its walls, when it may be said to evert itself. The mucous 

 membrane will then be on the outside. The accident is of very rare 

 occurrence, and is usually brought about by the pains of parturition. It 

 may, however, result from other causes where violent straining is excited, 

 and the contents of the abdomen are forcibly pressed against the bladder 

 at a time when possibly the opening into it is abnormally dilated. 



Symptoms. — A fleshy-looking mass, more or less rounded, projects 

 through the vulva, varying in appearance according as the accident is 

 recent or of some duration ; at first it is a pale pinkish-red hue, darkening 

 with exposure to a bluish or blackish red colour. The protruding organ 

 has been mistaken for the foetal envelopes, and fatally injured by an 



