RECENT LITERATURE OF SECRETING GLANDS. 403 



with which in some cases involuntary muscular fibres, running circularly, are intro- 

 duced, is added. In the sweat glands, the muscular fibres run longitudinally, and lie 

 between the basement-membrane and the epithelium of the tubular alveoli. The 

 epithelium-cells are usually flattened at the commencement of the duct, where these 

 emerge from the alveoli, and are columnar in the rest of the duct. In some glands 

 the columnar cells of the ducts exhibit a peculiar striated appearance (fig. 463, d) in 

 the part of the cell next to the basement-membrane, and the alveolar cells may also 

 exhibit a similar appearance, but far less distinctly. 



Mechanism of the discharge of secretion from a gland. Although no 

 doubt dependent ultimately upon physical and chemical conditions, it is not known 

 precisely in what way the discharge of secretion from the gland-cells, and eventually 

 from the gland, is effected. The forces which produce the discharge are, however, 

 considerable, and are influenced as we have seen through the nervous system. In 

 the cutaneous glands of the frog, Strieker and Spina have noticed that irritation of 

 the nerves is followed by swelling and enlargement of the previously flattened cells 

 of the gland, and that this enlargement causes a discharge of secretion from the 

 mouth of the duct. The swelling is produced by an accumulation of fluid, derived 

 from the plasma of the blood, within the cells, and when these come again to the 

 condition of rest and resume the flattened form, the fluid is supposed to pass from 

 them into the cavity of the alveolus, carrying with it the materials of secretion 

 extracted from the cells. If the glands are again stimulated the same process is gone 

 through, and in this way it is supposed an intermittent discharge may be caused. 

 There is no evidence, however, to show that similar changes occur in other glands, 

 nor is it explained how it happens that the water of the plasma should pass into the 

 cells only under the influence of excitation. 



The observations of v. Gehuchten seem to point to the vis-a-tergo of the accumu- 

 lating secretion as the main agent in effecting the discharge of the secretion from 

 the cells. The discharge from the ducts of a gland is no doubt partly due to the 

 vis-a-tergo of the accumulating secretion, partly to the peristaltic contraction of the 

 muscular tissue in the wall of the duct (where this tissue exists). 



BECENT LITERATURE. 



Biedermann, W. , Ueber morpholof/iscke Verdnderungcn der Zungendrusen des Frosches bei 

 Iteizung der Driisennerven, Wiener Sitzungsber., Bd. 86, 1882 ; Zur Histoloyie und Physiologic der 

 Schleimsecretion, Tagebl. der 59. Versamml. d. Naturforscher u. Aerzte zu Berlin, 1886. 



Bizzozero, G., u. Vassale, G., Ueber den Verbrauch der Driisenzellen der Saugethiere in 

 encachsencn Drusen, Centralblatt f. d. medic. Wissenschaften, No. 4, 1885 ; Ueber die Erzeugung und 

 die pht/sioloyische Regeneration der Drusenzellen bei den Sdugetkiercn, Archiv f. pathologische Anat., 

 Bd. 110, 1887. 



Bizzozero, G-., Ueber die Schlauchformigen Drusen des Magendarmcanales und die Beziehungen 

 ihres Epithets zu dem Oberjliichenepithel der Schleimltaut, Arch. f. mikrosk. Anat., Bd. xxxiii., 1889. 



Chievitz, Entwickeluiigsgeschichte der Speicheldrusen, Archiv f. Anat. u. Physiol., Anat. Abth. , 

 1885. 



Dewitz, Ueber das vcrschiedene Aussehen der gereizten und rulienden Drusen von Zehenbatten 

 des Laubfroschns, Biolog. Centralb., 1883. 



Flemming;, W., Ueber Ban und Eintheilung der Drusen, Arch. f. Anat. u. Physiol., Anat. Abth., 

 1888. 



Gehuchten, A. van, Recherclies histologiques s. Vappareil digestif d. 1. larve d. I. Ptycoptera 

 contaminata, La Cellule, t. vi. , 1890 ; Le mecanisine de la secretion, Anat. Anzeiger, Jan. 1891. 



Gilson, G., RecJierches sur les cellules secretantes, La Cellule, t. vi., 1890. 



Hofer, B. , Untersuchungen uber den Ban der Speicheldrusen und des dazu gehorenden Nerven- 

 apparates con Blatta, Nova Acta Academise Leopoldino-CarolinEe, Bd. 51. 1887. 



Klein, E., On the Lymphatic System and the Minute Structure of the Salivary Glands and 

 Pancreas, Quart. Journ. Microsc. Scienc. , Bd. 22, 1882. 



Kniippel, A., Ueber Speicheldrusen von Insecten, Inaug. Diss., Berlin, 1887. 



Kowalewsky, N., Ueber das Blutyefasssystem der Speicheldrusen, Archiv f. Anatomic und 

 Physiologic, Anat. Abthlg., 1885. 



Kultschizky, N., Zur Lehre vom feineren Bau der Speicheldrusen, Zeitschr. f. wissensch. Zool., 

 Bd. xli., 1884. 



