PHYSIOLOGICAL ANATOMY OF THE URINARY PASSAGES. 369 



two crural, the two brachial and the two carotid arteries, he increased the 

 blood-pressure about one-half, and the quantity of urine discharged in a min- 

 ute was immediately increased by a little more than fifty per cent. In 

 another animal, he diminished the pressure by taking blood from the jugu- 

 lar vein, and the quantity of urine was immediately reduced about one-half. 

 He also showed that the increase in the quantity of urine produced by ex- 

 aggerated pressure of blood in the kidneys could be modified through the 

 nervous system. The nerves going to one kidney were divided, which pro- 

 duced an increase in the arterial pressure and a consequent exaggeration in 

 the quantity of urine from the ureter on that side. The pressure was then 

 farther increased by stopping the nostrils of the animal. The quantity of 

 urine was increased by this on the side on which the nerves had been divided, 

 but the pain and distress from want of air arrested the secretion upon the 

 sound side. 



When irritation is applied to the floor of the fourth ventricle, in the median 

 line, exactly in the middle of the space between the origin of the pneumo- 

 gastrics and the auditory nerves, the urine is increased in quantity and be- 

 comes strongly saccharine. When the irritation is applied a little above 

 this point, the urine is simply increased in quantity, but it contains no sugar ; 

 and when a puncture is made a little below, sugar appears in the urine, 

 without any increase in the quantity of the secretion (Bernard). It has also 

 been observed that section of the spinal cord in the upper part of the dor- 

 sal region arrests, for a time, the secretion of urine. 



Other physiological conditions that affect the urinary excretion influence 

 the composition of the urine and the quantity of excrementitious matters sep- 

 arated by the kidneys. These will be fully considered in another place. It 

 is sufficient to remark, in this connection, that during digestion, when the 

 composition of the blood is modified by the absorption of nutritive matters, 

 the quantity of urine usually is increased. This is particularly marked when 

 a large quantity of liquid has been taken. 



Inasmuch as the excrementitious matters eliminated by the kidneys are 

 being constantly produced in the tissues by the process of disassimilation, 

 the formation of urine is constant, presenting, in this regard, a marked 

 contrast with the intermittent flow of most of the secretions proper as distin- 

 guished from the excretions. It was noted by Erichsen, in a case of extro- 

 version of the bladder, and it has been farther shown by experiments upon 

 dogs, that there is an alternation in the action of the kidneys upon the two 

 sides. Bernard exposed the ureters in a living animal and fixed a small, silver 

 tube in each, so that the secretion from either kidney could be readily ob- 

 served ; and he noted that a large quantity of fluid was discharged from one 

 side for fifteen to thirty minutes, while the flow from the other side was slight 

 and in some instances was arrested. The flow then began with activity upon 

 the other side, while the discharge from the opposite ureter was diminished 

 or arrested. 



Physiological Anatomy of the Urinary Passages. The excretory ducts 

 of the kidneys, the ureters, begin each by a funnel-shaped portion, which is 



