XXXVII.] UMBILICAL CORD AND PLACENTA. 



395 



amount of somewhat loose connective tissue, and sections of the 

 ducts (D). The sections should be made so as to include the 

 nipple, when the larger ducts with their dilations will be seen. 

 The ducts are large between the lobules, and within the latter the 

 course of the finer ducts can readily be traced. 



(b.) The globular acini, with a basement membrane lined by a 

 single layer of somewhat flattened or cubical epithelium. In the 

 inter-alveolar tissue many leucocytes and granular cells. 



2. Active Mammary Gland (Safranin) (H). 



(a.) Study specially the acini Observe the large and tall 

 columnar cells lining the acini, and in some of the cells clear 

 refractive granules of fat. The lumen is wide, and is usually 

 partially filled with the debris of the secretion-milk. Osmic acid is 

 a good agent for showing the presence of fatty granules (fig. 366). 



3. Colostrum (H), i.e., the first milk secreted after delivery. 

 If this can be obtained, examine it, and note, in addition to the 

 ordinary milk-globules (Lesson I. 3), large coarsely granular nucle- 

 ated refractile cells colostrum corpuscles. The granules are 

 sometimes pigmeiited, and are fatty (fig. 367). 



UMBILICAL COED AND PLACENTA. 



4. T.S. Umbilical Cord. Harden this in Muller's fluid or 

 alcohol. Make T.S. by freezing, and stain them with hsematoxylin 

 or ] )icro-carmine. Methyl-violet is also a good stain. 



(a.) Note on the outside of 

 the circular mass of tissue a 

 thin layer of flattened cells 

 derived from the amnion. 



(b.) The cord itself, composed 

 of Wharton's jelly, enclosing 

 usually two umbilical arteries 

 and a single vein with very 

 thick muscular coats. They 

 are completely surrounded by 

 AVharton's jelly, which, how- 

 ever, in a cord at full time is 

 very largely composed of fibrous 

 tissue. Still numerous branched 

 connective tissue corpuscles exist 

 in the meshes, and there are 

 also present numerous lymphoiJ-looking cells (Lesson XII. 10). 



5. Fresh Placenta (H). Tease a fragment of a placenta in 

 normal saline. Note the vitli, each long, tapering, and branched. 

 In the interior capillary loops which occupy the greater part of the 



FIG. 368. Human Flaceiita Villi. 

 vessels black. 



Blood- 



