578 THE POSTERIOR PITUITARY AND THE NERVOUS SYSTEM. 



exposed to the action of the oxidizing substance of the plasma, and 

 thus to render the dendrite functionally active : i.e., able to trans- 

 mit or receive nervous impulses. When the gemmules are retracted 

 or collapsed, therefore, functional activity is in abeyance, as during 

 sleep, anesthesia, etc.: i.e., they are unable to transmit or receive 

 impulses. 



This tends to show that none of the gemmules serve per 

 se to transmit impulses, and that the dendritic tips must alone 

 be endowed with this function. That such is the case seems to 

 us suggested by Fig. 2 on the plate opposite page 550, which 

 exemplifies the condition of a dendron before the engorgement 

 induced by ricin has become far advanced: i.e., at a time when 

 the dendron's lumen has not as yet become completely blocked. 

 The two central dendrites may be seen to terminate with bulb- 

 ous tips, while the remaining gemmules immediately adjoining 

 the latter are not apparently enlarged. This would point to 

 the enlarged extremity as a dissimilar structure in respect to 

 the gemmules, a terminal organ as it were. Again, the gem- 

 mules and terminal organ would have presented a certain de- 

 gree of resemblance under the influence of the engorgement 

 under the action of poisons, had they been similar; their ap- 

 pearance, on the contrary, suggests dissimilarity. Berkley 

 states that, "so far as the end-apparatus of the collaterals from 

 the psychical cells is concerned, the terminations of the inter- 

 mediary cells, the fibers entering from the medullated masses, 

 all have the same end-apparatus, which consists solely of a 

 simple freely terminating bulbous ending, situated upon the 

 extremity of the finest branches of the nerve-fibers." As he 

 then refers to figures in one of his illustrations which represent 

 axons supplied with bulbar extremities, we infer that it is to 

 the dendritic terminals that he alludes, and not to those of 

 the gemmules, as a broad application of his preceding para- 

 graphs might suggest. If the bulbous terminals of the entire 

 dendrite as well as the axon are referred to, the quoted lines 

 afford additional evidence tending to show that the dendritic 

 extremities alone transmit or receive impulses. Indeed, in 

 the article in which chronic alcoholic poisoning is studied, 

 Berkley remarks: "The process of tumefaction always appears 

 to begin at or near the fine extremity of the dendron, be it the 



