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Retzius, Bizzozero, and many others it is now known that in the embryo and adult, in plant and animal, vertebrates and invertebrates, all kinds of cells, before their protoplasm undergoes division, show complicated changes of their nucleus, leading to division. This manner of division is called the indirect division or karyokinesis.It has been observed by Mayzel, Schleicher, and Flemming, that the nuclear fibrils show movement, hence the name karyokinesis. This ELEMENTS OF HISTOLOGY.[chap. n. circulating blood or in blood that has just been removed from the vessels. Their substance is transparent granular-looking protoplasm, containing larger or smaller bright granules. These granules are either of a fatty nature, or, as in some kinds of blood, notably horses', are of a reddish colour, and these corpuscles are supposed by some observers (Semmer and Alexander Schmidt) to be intermediate between red and white corpuscles. The protoplasm of the colourless corpuscles contains glycogen (Ranvier, Schafer).In the blood of lower vertebrates the colourless corpuscles are considerably larger than in mammals. But in all cases they consist of protoplasm, include one, two, or more nuclei, and show amoeboid movement. This may be

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Medullomyoblastoma is a rare histologic variant of medulloblastoma. Of the 20 cases reported in the literature, 19 were in children ages 2.5 to 10.5 years and one was in a 26-year-old woman. In the reported adult case the myogenic component of the tumor was leiomyosarcomatous. The authors report a case of medullomyoblastoma with a rhabdomyosarcomatous component in a 40-year-old man with light microscopic, immunohistochemical, and ultrastructural findings. The histogenetic theories regarding this tumor include that it is a teratoma, or that the myogenic component arises from the perivascular or leptomeningeal ectomesenchyme, or pluripotential neuroectodermal cells, or endothelial cells. The authors' findings do not elucidate the histogenesis but argue against an endothelial origin of the rhabdomyoblastic component.

Development of Lymphatic Capillaries 54 IV. Blood-vessels of the Serous Membranes 58 SECTION II. PATHOLOGICAL CONDITIONS. on the peritoneal surface of the septum cisternae lymphaticae magnse of the frog, especially on the endothelial cells which surround, or more correctly speaking, which line the stomata first described by '^Dogiel and Schweigger-Seidel. S These authors found on the peritoneal surface of the septum of female frogs, dviring the spawning season, ciliated endothelial cells of a nearly cylindrical shape, in small groups near the stomata. I shall J turn to the stomata afterwards. At present I wish only to mention \ that during the winter months, in some septa besides the germinating r^mostly ciliated endothelial cells, there exist shorter or longer tracts, ".which project more or less freely on the peritoneal surface, and which jf are covered with polyhedral, sometimes ciliated endothelial cells. Ludwig and Schweigger-Seidel first called attention to the difference which exists as regards the endothelium of different portions of the peritoneal surface of the centrum tendineiun of the diaphragm of rabbits. These authors have shown that the endothelial cells, which are situated over the straight lymphatic channels, between the tendon bundles, are of a smaller size than the endothelial cells which lie over the tendon bimdles themselves. They assert also that there exist sometimes groups of lymphoid corpuscles, which are continuous with, or properly speaking, derived from, those stripes of small endothelial cells previously mentioned. I am able not only to confirm this latter observation, but also to GERMINATING ENDOTHELIUM. 7 complete it to the extent that there exist groups or tracts of germinating endothelium in rabbits as well as in guinea-pigs, cats, dogs, and monkeys, which, as we shall see afterwards, stand in an intimate relation to lymphatic vessels. Somewhat different in its arrangement is the germinating endothelium of the mesentery of frogs, cats, dogs, and monkeys, viz. in these membranes they occur only in groups of less than five endothelial cells, mostly two or three. They are also of a polyhedral shape, consisting of a distinctly granular protoplasm, with a constricted or double vesicular nucleus ; their size is considerably smaller than that of the common endothelial plates surrounding them. On fresh preparations, which have been moimted in serum with great care, they appear as granular bodies projecting from the surface like buds; on preparations stained with silver solution, they appear generally beset with brownish granules. There exists a great variety as regards the number of such groups in a given field. Searching the surface of the membrane under a magnifying power of about 200, one passes two or three fields where there are no groups ; whereas, in a neighbouring field one meets with half-a-dozen or even a dozen of them. They are to be found over those parts which contain large blood-vessels qiute as often as over the intermediate portions. These structures are not to be confound...

Summary.-Blood lymphocytes from 47 patients with lung carcinoma have been tested for cytotoxicity against cells isolated from the autologous tumour. Significant cytotoxic potential was found in 15 cases. The effectors were also tested against allogeneic tumour targets from lung and other sites. Reactions were only rarely detected (2/32 positive against lung and 1/13 positive against non-lung cells). The restriction of cytotoxicity to the autologous combination was also apparent in in vitro-generated effectors. Blood lymphocytes were co-cultivated with autologous tumour and subsequently tested against autologous or allogeneic targets. Cytotoxicity was found in 13/17 lung tumours against autologous tumour, with no reactions recorded against allogeneic tumour targets, but one case positive against the K562 cell line. These data suggest either the expression of individually distinct antigens on human pulmonary neoplasms, or the requirement for histocompatibility between target and effector in cytotoxicity reactions in man, and therefore differ from previously described patterns of lymphocytotoxicity against human tumours.

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