The Urine. 211 



when urine is flowing along it, is a closed channel, the 

 walls of which are in apposition. The mare after urinating 

 spasmodically erects the clitoris, the use of which it is 

 difficult to see ; it may be due to the passage of a hot 

 alkaline fluid over a remarkably sensitive surface. 



The horse can under ordinary circumstances only pass 

 his urine when standing still, though he can defalcate while 

 trotting ; but a mare, if considerably excited, can empty the 

 bladder even at a canter. 



In the ox, owing to the curves in the urethral canal, the 

 urine simply dribbles away, being directed towards the 

 ground by the tuft of hair found on the extremity of the 

 sheath. The ox can pass his urine while walking. 



The cow sinks her body to urinate, but instead of 

 extending her hind -limbs as does the mare, she brings 

 them under the body, at the same time raising her tail. 



The centre for the renal nerves is said to be in the floor 

 of the fourth ventricle, puncture of which part produces 

 diabetes. 



The nerves supplying the neck of the bladder originate 

 in the sacral region, and injury to the part produces 

 paralysis of the neck and constant dribbling of urine. 

 Severe injury to the spinal cord may exist far forward with- 

 out any immediate sign of bladder trouble being present ; 

 in such cases the work is carried on by the centre in the 

 lumbar cord. 



Abnormal Constituents and Urine-testing. 



Although I have made it a rule throughout this work to 

 avoid the introduction of methods of inquiry, for the 

 reasons stated in the preface, yet I feel compelled to depart 

 from this course in the present instance, as the question of 

 the composition of the urine in health and disease has a 

 most important clinical aspect. I shall here mention the 

 abnormal substances found, and afterwards deal generally 

 with urine-testing. 



Albumin. — At least two forms of albumin may exist in 

 the urine, viz., serum albumin and serum globulin, and to 



14—2 



