CH. XVI.] 



NISSL'S GRANULES 



193 



and during the act of secretion they are discharged and converted 

 into constituents of the secretion. It is stated by some observers 

 that the Nissl granules are used up during the discharge of energy 

 from nerve-cells, and it certainly is the case that if the cells are 

 examined after an epileptic fit, in which there has been a very massive 

 discharge of impulses, the Nissl granules have disappeared, or at 

 least broken up into fine dust-like particles, so that the cell presents 

 a more uniform blue staining. This is called chromatolysis (see 

 fig. 186). It is, however, doubtful whether this is due to a transfor- 

 mation associated with intense activity, or whether it may not be 



Fto. 186. Nissl's granules. A. Normal pyramidal cell of human cerebral cortex. B. Swollen rede* 

 matous pyramidal cell from a case of status epilepticus. Notice diffuse staining, and absence of 

 Nissl's granules ; the nucleus is enlarged and eccentric. The lymph space around the cell is 

 dilated. C. Pyramidal cell of dog after ligature of vessels going to brain and consequent anaemia. 

 Notice great swelling of the nucleus, and advanced chromatolysis, most marked at the periphery 

 of the cell. 700 diameters. (After Mott.) 



caused by venosity of the blood. The cells are very sensitive to 

 altered vascular conditions ; ansemia, for instance, produces a similar 

 change accompanied with swelling of the cell, and swelling and in 

 extreme cases extrusion of the nucleus. 



The most convincing observations in reference to the influence of 

 fatigue in producing chromatolysis have been made on bees ; their 

 nerve-cells are rich in chromophilic material when they are about 

 to leave the hive in the morning. In the evening, after a hard day's 

 work, this material is much reduced in quantity. 



By this sensitive method neurologists have been able to identify 

 changes in the cells which could not be detected by the previous 

 methods of staining. Thus the cells have been examined in various 

 diseases, or after being subjected to the action of certain poisons, and 



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