ORGANS OF THE BODY. 



543 



several primordial ova. In this way. follicles are eventually formed in 

 their most rudimentary form. 



On the external side of the Wolffi.an body this epithelium dips down to 

 form a groove. From this, again, a canal is formed subsequently, the 

 canal of Mutter ( Waldeyer\ and from it the Fallopian tube and uterus 

 are developed. 



Several very important points have recently been brought forward by 

 Pfliiger in regard to the follicles, 

 which enable us the better to com- 

 prehend some statements made long 

 ago by Valentin and Billroth, which 

 had almost sunk into oblivion. These 

 have since been confirmed by many 

 other observers, among whom may 

 be named Borsenkorp and Spiegel- 

 berg, His, Letzerich, Langhanns, 

 Freij, Koelliker, and Waldeyer. 



According to Pfluyer's investiga- 

 tions the Graafian follicles are 

 secondary formations. He asserts 

 that they take their origin from ob- 

 long or irregular aggregations of cells 

 by a process of constriction affect- 

 ing the latter at various points. To 

 these collections of cells the name 

 of primordial rudimentary follicles, 

 or, more briefly expressed, " ova 

 chains" (Eistrangen), has been given 

 (fig. 535). They contain besides 

 peripheral cells of small size and 

 pale colour (the elements of the 

 future membrana granulosa), the 

 primordial ova. These are situated 

 in the axis of the group, and may 

 be distinguished by their greater 

 magnitude and granular protoplasm. 

 Their existence, therefore, anterior 

 to the formation of the follicle, is a point about which there can be 

 but little doubt. These cell-gronpings are sometimes enclosed in a homor 

 geneous membrana propria, giving rise to regular tubular structures, as in 

 the cat. This may be absent in other cases, as in the calf. The arrange- 

 ment of newly-formed follicles which, instead of occurring singly, appear 

 still in groups, or ranged like beads on a string (Follikelketten), is thus 

 easily understood as regards the mode of their development. The primor- 

 dial ovum possesses farther vital contractility, and multiplies by segmen- 

 tation (Pfliiger). 



It is only at certain points, however, that at this period we come upon 

 these " ova chains," which explains the fact of their having so long 

 remained undiscovered. 



Pfliiger states that he has satisfied himself that in the kitten, four 

 weeks after birth, the period for finding these primordial tubes is already 

 passed. But towards the time of casting their young the formative 

 energy awakes afresh in the ovary of the mammal, and not only are 



Fig. 535. Chains of follicles from the ovary of a 

 calf. 1, containing ova in process of develop- 

 ment; and, 2. showing gemmation to form* 

 Graaffian follicles. 



