No. 2.] CHANGES IN NERVE CELLS. 



105 



Secular changes in liver cells of frogs have been studied 

 with great care by Alice Leonard (41). The cells are found 

 to vary greatly in size at different seasons, reaching a maxi- 

 mum in November, and shrinking to less than one-fifth this 

 size by April. The nucleus, on the contrary, is smallest in 

 November, 6 ;i in diameter, and largest, 'j.6 fi, in April. The 

 protoplasm may be said almost to disappear during the winter, 

 pigment in the cells showing an increase in amount at the same 

 time. By this extreme change, an action of different stains 

 upon constituents of the cell-protoplasm is brought to light ; 

 viz. that eosin (41, p. 34) stains carbohydrate, and nigrosin 

 albuminous material. 



There is seen to be little agreement as to the action of gland 

 cells, and more can scarcely be expected as to results until 

 methods become better known, more precise, and more con- 

 sensus as to their use is reached. So far little more can be 

 said to be established than that during rest the cells become 

 filled with granules, and that during secretion these granules 

 pass out, generally leaving the cell shrunken. A few obser\'-a- 

 tions indicate a probability that these granules arise in the 

 nucleus. One writer (60) affirms the fact. The fact that nuclei 

 are sometimes extruded during active secretion, as occurs in 

 mammary glands and those of the digestive tract in insects 

 (Van Gehiichten), is not necessarily opposed to this view. 

 Whether the nucleus swells, or shrinks, or changes in staining 

 properties is a question of dispute.^ 



Muscle. 



"A simplified view of the histology of the striped muscle 

 fibre" advanced by Melland (49) in 1885 is the one adopted in 

 the following discussion. According to this we have to deal 

 with a highly specialized cell-reticulum with fibrils arranged in 

 cross and longitudinal series. This is supposedly the contrac- 

 tile mechanism. Between the meshes of this reticulum is a 

 structureless, semifluid muscle plasma. Scattered through the 

 muscle substance or lying just underneath the sarcolemma are 



^ From the first the writer has intended to repeat the more important experiments 

 in this field of gland histology, and until an opportunity for doing so presents itselt 

 further discussion of the subject will hardly be profitable. 



