Generally, of all the visceras, the ovary is the commonest place for cyst-formation, and the majority of all the ovarial cysts are multilocular pseudomucinous forms. Lieppert states that it occupied 53.6% and by Stubler and Branders, 30.6% and by Pfannestiel, ca. 2/3 of all the ovarial cyst. ･ In many cases, it is one sided (ca. 90%) and moreover is pedunculated, and as the epitherial proliferarion of the tumor is almost unlimitedly repeated and so it is, indeed, possible to become a wonderful size. We have never seen any other tumor which can grow so large like the ovarial pseudomucinous tumor. Therefore, when I consider the reason that, even now, we sometimes meet with a gigantic ovarial cyst like these, considering from the side of patient, I can cite the following facts ; first : the extreme terror of surgical operation, second : they have been left behind in the march of progress of civilization, and third : the poverty of their family, etc. In my cases, all the patients are either country people living far off from the civilized city, or those disliked the operation, and on the other side, the wrong diagnosis of the doctor and the midwife, which took it for pregnancy. These facts should be also considered in connection with it. Probably it may not be an error to attribute one of these reasons in Case 1. Such a monstrous tumor looks as if it occupies the whole abdorninal cavity and it extremely presses the abdominal visceras and diaphragma. The Kaufmanns case mentioned previously shows that the height of its diaphragma is in the Ist intercostal space in the left side and the 4th rib at the right. Consequently the thoracic visceras are also pressed and causes some trouble in the heart and lungs. These disorders are, however, gradually recovered after removal of the cyst, as all of my cases have proved. The carrier of the head and extremities are rather the appendages of the tumor. Still the patient becomes very thin and her face characteristically shows the so-called "" Facies ovarica "" which is quite different from cachexy, but a similarity of feature is observed in those who are suffering from the said disease and it appears as if they are related each other. The development of the cyst is generally very slow but its monstrous one is rapidly enlarged at certain period. It appears at any age, old or young, mostly between 20 and 50, and especially Mainzer, Olshausen and the author have reported cases of very aged woman. The size of cyst varies from the very small to the marvellous monster one and it is not infrequently reported as mentioned before that the weight of cyst exceeds the body-weight. The gigantic cyst, of course, interrupts pregnancy, delivery and puerperium. The monstrous cyst consists of the so-called a large main chamber and many small accessory chambers and some are very tense in consistence. It, is mostly spherical in shape and all of my cases are like irregular gourd which is generally seen in literature. The surface of cyst is generally white-pearty, glittering appearance, but following the alteration of the content, of each chamber, its surface changes to yellow, black and yellowish-brown or dark red-color. The contents of the cysts are changeable ; sometimes are very diluted serous or mucinous but generally thick mucous and frequently become very viscid. The monstrous cyst posseses various substances secondarily. As to the constitution of the contents, Scherer and Eichwald ever said that it consists of paralbumin and metalbumin but as a matter of fact there exists no albumin. Hammarsten named it pseudomucin, illustrating from his view point ; Pfannenstiel noted that it is not so simple substance and Mizukoff proved the existence of paramucin. Histologically the lumen of cyst is lined by a single layer of irregularly arranged cylindric epithelium having nuclei and glittering protoplasmas that lie at the bases of the cells and they quite resemble to the germinal epithelium of the intestine. Lahm reported that there are rarely seen the dark black colored spots on the inner surface of the cyst lumen and these are consisted of the cells which contained lipoidofuchsin-group-pigments. No particularity was noticed in my cases. There are also found various secondary changes in ca. 60% of all the cases. The torsion is said to occur in from 10 to 20% of cases, and sometimes it fil]ally goes to the resection of the peduncle. The rupture of cyst-wall is not so infrequent and it results the seed-metastasis of the benign tumor of same kind. Metastasis after removal of the cyst is very rare but Olshausen and Baumgarten reported the benign metastasis in the parietal cicatrix and Schrader and Polano, the malignant metastasis. The perforation of cyst to the adjacent viscera is very infrequent Hemorrhage, infection, suppuration and calcareous infiltration are sometimes observed. Again, the complication of pregnancy also cannot be excepted and this is also seen as that of dermoidcyst but its occurrence is ca. 2%. Pfannenstiel marked that pseudomucinous cyst is frequently combined with the dermoidcyst. It is, however, infrequent (4- 5%) from the stand point of my experience and I can not agree with the view that the cyst-formation of dermoidcyst is proliferated from the pseudomucinous cyst. The most frequent occurrence in the secondary changes is the adhesion to the adjacent visceras. But it is not serious and even if it is in an advanced stage can be removed easily. Of all the changes, the malignant degeneration is the most troublesome (according to Stubler and Branders it is 6.7%) and its etiology is still unknown. It is said that in long existence of the cyst in advanced aged woman, the malignant degeneration appears but in my case 3 in aged woman, though I devoted myself to its observation up to her death. I could not find any symptom of malignant degeneration, and the author had experienced in an aged woman of 86 years old whose ovarial cyst gradually grew in two or three years after it was found, and it attained to the size an adults head but he was unable to find the symptoms of malignant degeneration either. On the contrary, I even had an experience of miserable case of a woman of 23 years old in pseudomucinous ovarial cyst, who in only a year's progress after the cyst was found, it clearly happened to be carcinomatous degeneration and came to a sad end of exploratory laparotomy. How does this malignant degeneration occur ? As to its causes , I have contributed nothing but explain with many vague words which now require further investigation. I think that it can not be put in one class at all and I attribute this to an individuality of the cyst-carrier. It may be convenient to settle the question, if I explain it, as a cause of carcinoma also. Such a malignant degeneration, in this case, is very infrequent and it would certainly be an object of research in future. Finally, the auther expresses his respectful thanks to Dr. Ando, Professor of the Okayama Medical University for his revisal.
