DYNAMICS OF HISTOGENESIS 351 



bladder musculature presented a deep red appearance, resembling 

 somewhat cardiac muscle. The resistance to incision with the 

 scalpel had greatly increased. The bladder wall was 5 mm. thick. 

 The organ was highly vascular and the vesicular arteries and veins 

 w^ere abnormally enlarged when compared with those of a control 

 puppy. 



Histological ohservatio7is. The excised portion of the bladder 

 taken at the initial operation was normal smooth muscle of a 

 developing bladder (figs. 9 and 10) . The part of the bladder taken 

 at the second operation for sectioning and study showed definite 

 cross-striations and an increase in width and length of the muscle 

 fibers over that of the control (figs. 11 and 12). The physiological 

 reactions of a bladder that had been developed carefully to respond 

 to increased work two hundred times greater than that which it 

 w^as normally accustomed to, structurally reacted to do this work 

 by the transformation of the smooth young muscle cells into 

 striated muscle cells. The former type of muscle is incapable of 

 doing the work accomplished by the bladder under observation, 

 while the latter type possesses the capacity under the requisite 

 stimulus for prolonged rhythmic contractions and increased work. 

 The different degrees of energy possessed by the vesicular smooth 

 and cross-striated muscles here studied is purely a biomechanical 

 result corresponding to the differential amount of work that has 

 been expended in their formation. 



The complete study of the cytological and histological details 

 revealed by the transformed striated muscle of the bladder will be 

 reserved for a communication to be published later. The following 

 may be noted : The bladder musculature prior to the experiment 

 presented a syncytium with endoplasmic cells. The irregular, 

 wavy, and twisted nuclei were found within the granular cyto- 

 plasm. The spongioplasm was drawn out in delicate longitudinal 

 striations. The outer portion of the ectoplasm presents a modified 

 surface layer; there is, however, no specialized sarcolemma. The 

 endoplasmic units are comparatively narrow. 



The cross-striated vesicular musculature presents broad fibers 

 which form a network. The nuclei are centrally located and sur- 

 rounded by granular endoplasm. The isotropic and anisotropic 



