STRUCTURE OF PROTOPLASM 



or distortion) of the spherical alveoli into polyhedral or irregular com- 

 partments. Likewise the fibrillar or filar types may be interpreted as 

 similar more extensive modifications resulting in ruptures of the alveoli 

 and consequent finer or coarser indiscriminate aggregations of spongio- 



/ 



// 



FIG. 16. INTERSTITIAL CELL, FROM THE 

 TESTIS OF A TWENTY-ONE YEAH OLD 

 MAN, SHOWING GRANULAR AND FILA- 

 MENTOUS MITOCHONDRIA. 

 After Winiwarter. 



FIG. 17. A NEURON (GIANT PYRAMIDAL 

 CELL, OR CELL OF BETZ) FROM THE 

 CEREBRAL CORTEX OF MAN, SHOW- 

 ING THE NEUROFIBRILS. 



Bielschowsky technic. X 500. 



plasmic fibrils, or as the result of the coalescence of granules to form 

 fibrils. The distinction between fundamentally granular and alveolar 

 protoplasm, and secondarily derived types of granular and reticular 

 (fibrillar) protoplasm must be emphasized. In the performance of spe- 

 cific functions, certain cells elaborate secretory gran- 

 ules (gland cells, Fig. 14; nerve cells, Fig. 15; cells 

 with crystalloids, Fig. 16) ; others produce various 

 types of fibrils (e.g., nerve cell, Fig. 17; connective 

 tissue cells, and muscle cells) ; others elaborate fat 

 spherules (e.g., Fig. 18) ; and still others a canalicu- 

 lar (trophospongium) apparatus (Fig. 19). 



FIG. 18. DEVEL- 

 OPING FAT CELLS. 

 The fat droplets, 

 after extraction 

 with alcohol and 

 ether, appearing as 

 vacuoles. Hematein 

 and eosin. X 550. 



The foregoing description of protoplasmic struc- 

 ture pertains largely to the 'fixed' (dead) condition. In 

 this connection the terminology employed will continue 

 useful. But recent more refined physiochemical studies 

 of living protoplasm have aroused considerable skepti- 

 cism respecting the verity of actual specific structures corresponding to the 

 designations applied, more especially the spongioplasmic and limn network. 

 Perhaps the most that can be said with certainty regarding the fundamental 

 structure of protoplasm is to describe it as a 'granular gel.' Kite's studies 



