76 THE CORPUS LUTEUM OF PREGNANCY IN SWINE. 



that the nucleus of the fresh cell can sometimes hardly be seen. Some of these granules 

 are mitochondria; this may very easily be confirmed by making a preparation of fresh 

 teased cells with Janus green; this dye gives a vital stain of the mitochondria, as shown by 

 Bensley (1911). Other globules are fatty and are selectively stained, for the purpose of 

 analyzing the cell elements, by any of the usual methods for neutral fats, such as Sudan III 

 and osmic acid. The nature of the fatty substance of the lutein cell, as found in the horse, 

 cow, and sow, has been studied microchemically by Cesa-Bianchi (1908), who thinks it is 

 lecithin; the existence of this substance in the corpora lutea had previously been declared 

 by Loisel (1904) on the basis of test-tube analyses. A striking contrast to the statements 

 just made is offered by the report of J. W. Miller (1910) upon his studies of the human ovary, 

 in which he states emphatically that there is no substance in the fresh corpus luteum of preg- 

 nancy which gives the reactions of the neutral fats, and that such reactions are obtained only 

 during the puerperium; that is to say, in retrogressive corpora lutea. On the other hand, 

 the lutein cell of the cat is often so honeycombed with fat that the vacuoles resulting from 

 the action of alcohol and ether obscure the finer structure of the cell, so that I found it 

 impossible to use some cats' ovaries which were at hand, in studies to corroborate the results 

 of this research. 



The most comprehensive description of the fatty inclusions in the lutein cells is that of 

 Van der Stricht (1912), who worked with the ovaries of several species of bats. He finds 

 the cells of young corpora lutea loaded with osmic-blackening material, but that there is a 

 gradual decrease in amount of this substance until the latter part of pregnancy, when 

 globules again begin to be deposited. It is his opinion that the early deposit of fat is 

 epithelial in nature, representing a secretion of the corpus luteum, but that the later reappear- 

 ance of presumably fatty material is a sign of senescence of the tissue. I shall detail my 

 findings in the sows' lutein cells later; it suffices to say here that my preparations agree 

 fully with those of Van der Stricht, in spite of the great difference in zoological position 

 of the animals used. 



In celloidin sections of corpora lutea from animals containing fetuses less than 40 mm. 

 long, fixed with such common solutions as formalin, absolute alcohol, and bichloride of 

 mercury, in which neither the fat nor mitochondria are preserved; and in osmic acid prep- 

 arations, in which the fat is distinguished by its intensely black color, we find the peripheral 

 part of every cell, the exoplasm, occupied by a most curious maze of clear spaces, of protean 

 form, alternating with rings and rod-shaped masses of cytoplasmic material, which give 

 the cell an almost indescribable but striking appearance (fig. 4). 



Since these peculiar structures are found to be important guides in following the his- 

 tory of the lutein cell, it will be advisable to review briefly the conclusions of other investi- 

 gators regarding similar appearances in other cells. In 1898 Golgi reported that in prepara- 

 tions of nerve cells from the central nervous system, made by a method of chrome-silver 

 impregnation, he found the metallic substance deposited in the form of a network which 

 lay in the cytoplasmic portion of the cell. This structure he called the "Apparato reticulare 

 interne" About the same time Nelis and Holmgren both described net-like or strand-like 

 appearances in the cytoplasm of nerve cells, which were seen as unstained areas in sections 

 colored by dyes. Nelis called these structures "etat spiremateux du protoplasm" and 

 Holmgren applied the term "Saftkanalchen" and later "trophospongium" to the essentially 

 similar structures which he had found. 



As these canals began to be discovered in nerve cells of all kinds, and then in cells of 

 many other organs, their importance was recognized, and the many questions connected 



