DYNAMICS OF HISTOGENESIS 345 



8. The silkworm-gut loops, for fixing the flange of the tube 

 in place, tightened and the ends tied. 



EXPERIMENTAL RESULTS 



The volume of boric acid passed through the bladder was 

 gradually increased from April 3rd, five days after the supra- 

 pubic drainage tube had been inserted in the bladder, until 

 May 21st (table 1). The volume of the fluid was regulated 

 by means of a screw-clamp, and as soon as the puppy showed 

 signs of distress due to vesicular distention the circulation was 

 reduced or stopped completely until the fluid was passed by the 

 urethra. On April 3rd the experiment lasted for one-half hour, 

 during which time 20 cc. of fluid had passed through the bladder 

 and out through the urethra. The urethral passage of urine was 

 of the nature of clonic, short, rapidly recurring contractions. 

 One clonic spasm occurred every two minutes and each spasm 

 consisted of about ten short contractions. 



As time went on the clonic nature of the bladder contractions 

 was lost and a greater volume of fluid was passed with each 

 urethral relaxation. Corresponding to each individual contrac- 

 tion of the bladder, a complete urethral relaxation occurred. The 

 resemblance of the full contractions of the bladder to that of 

 the heart and the perfect coordinaton of urethral relaxation 

 and subsequent closure like a cardiac valve gave an ideal experi- 

 mental condition for inducing in the bladder the circulatory 

 changes found in the heart. A mechanical valve was occa- 

 sionafly used between the elevated pressure reservoir and the 

 mercury manometer. This device gave a still further resemblance 

 to the nature of the vesicular contractions, under a hydrody- 

 namic stimulus, comparable to that found in the heart. 



The mercury manometer, unfortunately, was not used through- 

 out the experiment. The striking results obtained later sug- 

 gested the use of this instrument in order to record more accu- 

 rately the vesicular contractions, their variation under varying 

 pressure and volume conditions, and their absolute inhibition by 

 withdrawing the stimulus by closing the screw clamp and stopping 

 the circulation. 



