DIUKESIS 



69 



ANNOTATION 



Obs. 42, 43. ' The secretion of the urine 

 may be influenced in two distinct ways by 

 changes in the composition of the blood : 



(1) ' The concentration of the colloids of 

 the plasma may be changed, and with it the 

 osmotic resistance to filtration through the 

 capsule. If the mechanical factor (filtration) 

 remains constant, lessened colloid concen- 

 tration must increase the filtrate.' 



(2) ' If there be present in the plasma, and 

 subsequently in the glomerular filtrate, any 

 solid which cannot permeate into the epithe- 

 lium of the tubules, it retards the absorption 

 of the fluid in which it is dissolved and thus 

 increases the urine.' 



The first part of the exercise produces 

 diminution of the colloid concentration in the 

 blood in the simplest possible way, namely, by 

 injection of isotonic salt solution (Ringer- 

 Locke fluid) into the blood. The quantity 

 you inject amounts to between ^ and ^ of 

 the total blood-volume of the cat, and with 

 this no diuresis follows for more than half 

 an hour or so, the injected fluid passing off 

 almost immediately into the lymph (see next 

 following exercise, exerc. XI). 



The injection of the hypertonic Na2S04 

 solution causes a tubule-diuresis (see quotation 

 2 above, and Cushny, Jnl. of Physiol, vol. 

 xxviii, p. 431, 1902). 



Obs. 44. The diuretic action of extract of 

 the posterior lobe of the pituitary body was 

 discovered by Schafer and Magnus {Jnl. of 

 Fhysiol. vol. xxvii, p. ix, 1901). 



Obs. 45. The diuretic effect of the xanthine 

 compound, caffeine, was examined first by 

 Schroeder, Arch. f. exper. Path. u. Pharm. 

 xxiv, 39, 1887. Its diuretic action is best seen 

 in rabbit and man, and is said not to occur in 

 the cat, but under the above conditions of 

 experiment it occurs regularly. It is best to 

 make the observations with pituitary extract 

 (infundin) before that with caffeine, because 

 experience with the experiment shows that 

 infundin is apt to fail in producing diuresis 

 if administered soon after the caffeine citrate 

 diuresis has been evoked. 



Consult, on the whole of the diuresis part 

 of the exercise, Cushny, Secretion of Urine, 

 London, 1917. 



PLATE V 

 Diuresis Experiment (Exerc. X). 

 Fig. 1. Operation, 1st stage ; pubic symphysis cleared. 



Fig. 2. Operation, 2nd stage; pubic symphysis removed ; urethra exposed and incised for 

 insertion of cannula. 



Fig. 3. Glass cannula for urethra, actual size. 

 Fig. 4. Arrangement for observing urinary flow. 



Fig. 5. Preparation of r. ext. jugular vein. Dotted black line gives mid-ventral line of 

 neck. Sh., top of r. shoulder. 



Influence op Cervical Sympathetic on Blood-supply of the Pinna (Exerc. XVII). 



Fig. 6. Tips of pinnae shaven, moistened with glycerine, and viewed by transmitted 

 light. L., left pinna with vascular dilatation ensuing after severance of left cervical sympa- 

 thetic trunk ; r., right pinna normal, right cervical sympathetic trunk being untouched. 



Fig. 7. Left pinna on faradization of distal (anterior) portion of cut left cervical 

 sympathetic trunk ; the network of vessels connecting central artery with marginal vein has 

 shrunken out of sight. 



