CYTOMORPHOSIS 



29 



ECTODERM 



branous labyrinth of 

 internal ear, and lining 

 of external ear. 



Epithelium lining 

 the central canal of the 

 spinal cord, and the 

 ventricles of the brain. 



All neurons and neu- 

 roglia of the nervous 

 system. 



Certain ductless 

 glands: pineal, posteri- 

 or (nervous) portion of 

 hypophysis, medulla of 

 suprarenal, and the 

 chromaffin system or 

 paraganglia. 



Possibly smooth mus- 

 cle associated with 

 sweat glands, and in 

 iris of eye. 



MESODERM 



ear (scalse tympani and 

 vestibuli). 



ENTODERM 



Bartholin in the fe- 

 male. 



Nuclei pulposi of 

 vertebrae, remains" ~t>f 

 the embryonic noto- 

 chord. (Of ectodermal 

 origin in the guinea 

 pig, according to G. 

 Carl Huber ; Anat. 

 Kec., Vol. 14, p. 217, 

 1918.) 



CYTOMORPHOSIS 



From the standpoint of the individual cells of tissues, histogenesis 

 involves progressive and regressive changes. This process may be desig- 

 nated as cytomorphosis (Minot). The gradual acquirement of definite 

 form by development is known as morphogenesis. Cytomorphosis in- 

 cludes several successive steps: (a) undifferentiated or embryonal stages; 

 (b) differentiated stage, during which the cell acquires and maintains its 

 maximum differentiation expressed structurally by a definite shape and 

 specific content and performs its specific function; (c) regressive, when 

 the function gradually wanes, and finally fails (reflected in coincident 

 protoplasmic alterations), the cell concerned suffering death and ulti- 

 mately removal from the body. 



With this preliminary general view of protoplasmic organization and 

 function (general cytology) we are prepared to approach histology proper. 



