112 GLANDS. 



tally detached from the walls of tlie ureters, bladder, 

 or urethra, and carried along with the urine in the 

 act of micturition. 



Development. The kidneys are developed behind the "Wolffi an 

 bodies, and entirely independently of them. They 

 take their origin from the mucous membrane of the 

 intestine, but the facts which we possess relative to 

 the transformations which these organs undergo dur- 

 ing their development, are not clearly enough esta- 

 blished to justify their introduction into this work. 



Preparations. The most useful preparations for the study of the 

 structure of the kidneys, are sections made with a 

 razor of kidneys rendered solid by boiling, and simi- 

 lar sections of fresh organs, as well as of those previ- 

 ously injected with fine colors ground in oil and well 

 rubbed up with pure oil of turpentine. 



[The most recent and valuable additions to our knowledge of 'the 

 minute structure of the kidney are due to the industry and talent of 

 the late Dr. C. E. Isaacs. His admirable paper, entitled " Researches 

 into the structure and physiology of the kidney (by C. E. Isaacs, 

 M.D., Demonstrator of Anatomy in the University of the City of 

 New York,") was read before the New York Academy of Medicine 

 in March, 1856, and in its numerous and excellent illustrations the 

 student will find great assistance in thoroughly comprehending the 

 minute anatomy of this organ. 



In view of the close and searching investigations of Dr. Isaacs 

 into the doubtful points in the minute structure of the kidney, and 

 his high character as a conscientious and skilful observer, I feel that 

 no apology is necessary for stating his conclusions at length, and 

 describing the ingenious and original methods by which he arrived 

 at them. 



He speaks of the " highly-elastic" nature of the basement mem- 

 brane forming the outer wall of the urinary tubules, and adds, " the 

 integrity of the tube being of the highest importance during life, 



