CHAP, iv.] METABOLIC PROCESSES OF THE BODY. 779 



centre of the lumen. Instead of one nucleus, two or even more are 

 now present, one well formed and normal being placed nearer the 

 base, and the others, often shewing signs of breaking or degenera- 

 tion, nearer the free end. Sometimes constrictions are seen 

 whereby the free peripheral portion of the cell, including one or 

 more of the nuclei, is apparently being separated from the basal 

 portion in which the remaining nucleus is lodged; and occasionally 

 portions or fragments of cells, nucleated or nucleusless, may 

 be seen lying in the cavity of the alveolus. In the cell-substance, 

 especially towards the free border of the cell, are numerous oil 

 globules of various sizes as well as granules or particles of other 

 nature ; some of the larger oil globules may be seen projecting 

 from the surface as if about to be extruded from the cell ; and in 

 the cavity of the alveolus oil globules with a thinner or thicker 

 coating of cell-substance are frequently present. 



Between such a fully loaded phase, and a completely discharged 

 phase, various intermediate conditions may be observed, the cells 

 being of greater or less height, containing one nucleus only or 

 more than one, the cell-substance occupied with few or with many 

 oil globules and other granules, and the free border more or less 

 jagged. _ 



Putting these facts together we may draw the following 

 conclusion, which is supported by other evidence, as to the 

 changes in the gland which characterize the loading and the 

 discharge. During loading the low flattened cell of the discharged 

 alveolus grows rapidly, elongating into the cylindrical form, and 

 the nucleus gives birth to two or more new nuclei. Mean- 

 while active metabolism is going on in the cell-substance, deposits 

 of fat as well as of other substances are taking place. By 

 what seems to be of the nature of an amoeboid movement, some of 

 the oil globules (and possibly other matters) are extruded from 

 the cell, much in the same way that an amoeba extrudes its ex- 

 crement. But besides this, a division of the cell, that is a separation 

 of part of the cell-substance with an included nucleus, takes place, 

 the daughter cell thus thrown off passing into the alveolus to form 

 part of the milk ; or a budding of the cell occurs, part of the cell 

 without a nucleus being similarly cast off and undergoing a 

 similar fate. In other words the secreting cell grows, loads itself 

 with metabolic products, and when loaded gives off bodily part of 

 itself to contribute to the secretion, part of the cell, and that part 

 always retaining a nucleus, remaining behind in order to secure 

 subsequent growth and further secretion. 



The secretion of milk differs from such a secretion as that of 

 saliva, and approaches the formation of sebum ( 437) inasmuch 

 as the transformed cell -substance is shed bodily to form part of 

 the milk. We say form part of the milk because this gross mode 

 of secretion is accompanied by the more ordinary mode. The cells 

 are at the same time in the more ordinary way discharging into 



