THE MITOCHONDRIAL CONSTITUENTS OF PROTOPLASM. 73 



(plate 1, fig. 3). Here the polarity, or the direction of secretion, is proximo-distal— 

 that is to say, from the basement membrane in the direction of the lumen — and is 

 indicated by the arrow. 



The mitochondria are, however, arranged entirely differently in the epithelial 

 cells of the intestine (plate 1, fig. 10). Champy (1911, p. 109) emphasizes the fact 

 that here they are sometimes gathered together at both poles of the cell, instead of 

 being heaped up only in the basal part, as in the pancreas. He interprets this as 

 meaning that the intestinal epithelial cells are polarized in two directions for 

 secretion and absorption. This is again represented by the arrows. 



In the thyroid (plate 1, fig. 8) mitochondria are not most abundant in the part 

 of the cells next the basement membrane as in the pancreas, parotid, and other 

 glands, but are much more numerous in the distal region of the cell next to the 

 lumen and the colloid substance. Bensley (1916, p. 50), on other grounds, has 

 concluded that the original proximo-distal polarity of the thyroid cells has been 

 reversed; that the normal direction of secretion is toward the basement membrane, 

 blood-vessels, and lymphatics, instead of in the direction of the intrafollicular 

 colloid as has been generally supposed, and he points out that the mitochondria 

 are also reversed. 



To sum up, in all glands where the polarity is proximo-distal (parotid, plate 1, 

 fig. 7), the mitochondria are accumulated in the proximal part of the cell; in cells 

 with double polarity (intestinal epithelium, plate 1, fig. 10), the mitochondria are 

 heaped up in the distal as well as in the proximal cytoplasm; and finally in cells 

 with reversed polarity (thyroid, plate 1 , fig. 8) , the mitochondria are gathered together 

 in the distal part of the cell instead of in the pro.ximal. 



In view of these facts one is tempted to inquire whether the clumping of the 

 so-called batonnets of Heidenhain, which (according to Regaud) are derivatives 

 of mitochondria, in the proximal parts of the cells of the kidney tubules (plate 1, 

 fig. 1), means that the original proximo-distal polarity of these cells is maintained 

 and that secretion takes place from the basement membrane toward the lumen. 



The question is, how universal is tliis apparent relation between mitochondria 

 and polarity? Are the mitochondria ever uniformly distributed in gland-cells 

 which are polarized? And, conversely, are they ever arranged in this way in cells 

 which are not polarized? It may be said that this accumulation of mitochondria 

 in the basal parts of the cells occurs in all zymogenic cells with proximo-distal 

 polarity which have been investigated in mammals. In addition to the examples 

 already cited the following may be mentioned: the cells of Paneth of the small 

 intestine, the chief cells of the stomach, the serous cells of Harder's gland, etc. 



I know of no instance in which the mitochondria are uniformly distributed in 

 definitely polarized gland-cells. It is certainly true that in gland-cells which are 

 unpolarized, or are but slightly polarized, the mitochondria are more uniformly 

 distributed throughout the cytoplasm. Thanks to the work of Nicolas, Regaud, 

 and Favre (1912fl, p. 201), we know the relations of mitochondria inhuman sebaceous 

 glands where the cells themselves are bodily transformed into the secretion and 

 are passed out through the ducts. The cells (particularly the older ones) well 



