66 



MANUAL OF HISTOLOGY. 



this figure may appear. The fusiform cell may be regarded as one of 

 these; besides being narrowed, it is fined off" at either end to a point 

 (fig. 44). 



The fusiform cell usually gives off at either end a thread-like process ; 

 but such filaments may occur in greater number in many animal cells, 

 and on their part undergo further ramification. It is in this way that 

 the stellate cell (fig. 45) is produced one of the most remarkable forms 

 in which the structure in question can meet the .eye. 



Fig. 43. Tall, narrow 

 cells, as found in 

 what is known as 

 cylinder or columnar 

 epithelium. 



Fig. 44. Fusiform cells 

 from immature con- 

 nective tissue. 



r. 45. Stellate cell 

 from a lymphatic 

 gland. 



3. But far more important than either shape or size is the substance of 

 the cell-body : in this the greatest variety is observed. 



Let us, take in the first place, young cells (fig. 46) : here we perceive 

 that the body is made up of a more or less soft, usually viscid and slimy 

 mass, containing in a transparent cementing medium a variable amount 

 of albuminous and fatty granules (a-g). This primordial cell-substance 

 is known at the present day by the name protoplasm (Remak and 

 Schvltze) borrowed from botany. It has also received from Beale, 

 Koelliker, and Dnjardin respectively, the names bioplasm, cytoplasm, 

 and sarcode. The chemical peculiarities of this proto- 

 plasm have been already referred to in 1 2, and we 

 shall be obliged presently to enter somewhat minutely 

 upon the consideration of its vital properties. It will 

 suffice to remark here, that it consists of an extremely 

 unstable albuminous compound, insoluble in water, but 

 which becomes gelatinous (or in some instances shrinks) 

 on imbibition of the latter : it coagulates further at a 

 low temperature and at death, so that only by the most 

 careful manipulation can it be examined in a normal 

 condition under the microscope. 



The amount of this protoplasm with which the nucleus 

 is enveloped is very variable, and consequently the size 

 and general appearance of cells. Our woodcut repre- 

 sents from a to d elements with a medium amount of 

 this substance; e, a larger proportion. Other cells are 

 observed to possess but a very small quantity of pro- 

 toplasm, as / and g, without having lost the capability, 

 however, of increasing in substance and subsequently 

 fulfilling all the purposes for which cells in general are 

 designed. As far as we know at present, a cell can never again be 

 formed from a nucleus which has quite lost its protoplasm. 



But if we turn now to mature or senescent cells, we frequently find 

 that the protoplasm of an earlier period of existence is replaced by 



Fig. 46. Different 

 kinds of cells with 

 nuclei and proto- 

 plasm ; lialf dia- 

 grammatic. 



