516 



GENERAL PHYSIOLOGY 



cells of insects (Fig. 256, II), and show that the exchange of sub- 

 stance between protoplasm and nucleus in secretion must be very 

 active. Corresponding to this is the fact observed by Heidenhain 

 ('83), that the nuclei of the cells of the salivary glands behave 

 essentially differently in the state of rest and that of extreme 

 secretion; in rest they send out pointed processes into the sur- 

 rounding protoplasm, while after continued stimulation they are 

 spherical and possess a smooth surface (Fig. 257). Further, Baum 

 ('86) has found that the nuclei of resting gland-cells stain much 

 more deeply with nuclear stains than the nuclei of gland-cells 

 that have secreted strongly a sign that the chromatic nuclein must 

 be destroyed in secretion. Lily Huie ('97) has also recently 



discovered very profound changes in the 

 nucleus during increased activity of the 

 cell in the secreting-cells of the insect- 

 eating marsh-plant Drosera, when the 

 latter is fed with egg-albumin. Green- 

 wood ('96) has likewise observed in the 

 colonial infusorian Carchesmm nuclear 

 changes which develop parallel with the 

 nutrition of the cell. The phenomena of 

 fatigue which Hodge, Lugaro, Mann and 

 others have observed in ganglion-cells 

 during excessive activity and with which 

 we have already become acquainted, 1 be- 

 long in the same category ; and the same 

 is true of O. Hertwig's observation ( '84) 

 that in eggs that are rich in yolk, the 

 nucleus always moves toward the place 

 where there is the greatest accumulation 

 of protoplasm. Finally, in a wide variety 

 of cells a remarkable change in the size 

 of the nucleus during cell-life 2 can be 

 observed, which can be brought about 



only by the nucleus receiving substances from the protoplasm 

 and giving off others to it. 



Usually, on account of the existence of a nuclear membrane, an 

 exchange of liquid substances only is possible between nucleus and 

 protoplasm. But in many cases where because of the failure or 

 disappearance of such a membrane solid masses may be exchanged, 

 many observers, such as Frommann, Auerbach, Leydig, Brass, 

 Stuhlmann, and others, have observed on the part of the nucleus a 

 direct ingestion or extrusion of granules and flakes. In certain 

 stages in the course of development of many cells there even occurs 

 regularly a disintegration of the nucleus into many small particles, 

 which are resorbed by the protoplasm. Thus, we recall the be- 



1 Cf. p. 464. 2 Of. Schwarz ('84, 2). 



FIG. 255. Ovum of Dytiscus 

 marginalia with two nutrient 

 cells above it. Nutrient mate- 

 rial is passing from the nutri- 

 ent cells into the ovum, and 

 the nucleus of the latter is 

 sending out pointed pseudo- 

 podia toward this material. 

 (After Korschelt.) 



