348 



MANUAL OF HISTOLOGY. 



Fig. 334. One of Rrunner's racemose glands from the human 

 being. 



Another peculiar species of tubular glands is presented in those in 



which the upper and 

 usually undivided blind 

 end is twisted into a con- 

 volution like a coil of 

 rope (fig. 331). To these 

 the suitable name of 

 " convoluted glands " has 

 been given (Knauel- 

 drusen of Meissner}. 



(2.) In a second group 

 of glandular organs we 

 meet the membrana pro- 

 pria under the elementary 

 form of the so-called open 

 gland vesicle, that is of a 

 short wide blind sac of 

 microscopic dimensions 

 (fig. 332). This struc- 

 ture may frequently be 

 very aptly compared to a short-necked flask with a wide body, whilst in 

 other cases it is more like a spheroidal berry or short blind gut. 



In this case the most characteristic points are the grouping of these 

 vesicles together. Such a group (which frequently attains considerable 

 dimensions) may form a complex gland still of microscopical minuteness, 

 or may be associated with other aggregations as a sub-division of an 

 organ (figs. 326 and 334), 



^ These aggregations are known under the names of lobuli or acini (1). 

 From these open vesicles a multitude of glands is built up, as, for instance, 



the so-called racemose, which, 

 with all their variety of general 

 figure and difference of size are 

 really under the microscope, 

 comparatively speaking, very 

 uniform as to structure. 



No very sharp line, however, 

 can be drawn between these 

 last described and the tubular 

 species. If the walls of the 

 latter be not smooth, namely, 

 and the membrana propria 

 bulges outwards in the form 

 of spheroidal projections, and 

 that a certain division of the 

 sac is combined with this, we 

 have as a consequence inter- 

 mediate forms which may witli 

 equal right be said to belong 

 to either species of gland. 



(3.) In a third species of glands we find a bounding layer of connective- 

 tissue in the form of a roundish capsule, closed on all sides, and fre- 

 quently of considerable size (fig. 335). Capsules of this kind get rid of 

 their contents either by rupture of their walls, known as dehiecence, by 



Fig. 335. Glandular capsules from the thyroid of a child, 

 a, ground-work of connective-tissue; b. the capsule 

 itself; c, gland cells of the latter. 



