102 PKOGRESS OF MICROSCOPICAL SCIENCE. 



the changes he records. They are well and clearly shown in the 

 drawings by which the paper is accompanied. As the author remarks: 

 " The symptoms in this case are very clearly explained by the morbid 

 changes that were formed in the medulla oblongata and spinal cord. 

 Lesions were traced in the nuclei of the facial, hypoglossal, vagus, 

 and spinal accessory nerves, and exjilained the symptoms of glosso- 

 pharyngeal paralysis. The extensive loss of substance in the anterior 

 and lateral grey substance of the cervical and dorsal regions, more 

 especially of the tradus intermedio-lateralis, explained feebleness of 

 respiratory movements, while progressive changes of similar character 

 in the lumbar and dorsal regions of coui'se explained the paralysis of 

 the upj)er and lower extremities." 



Bone- Absorption by means of Giant- Cells. — Mr. Alexander Morison,* 

 taking up the researches of Kolliker on absorption of bone by means 

 of giant-cells, finds, says Mr. Klein, in ' Medical Record,' July 8th, 

 1874, on examination of sections through the jaw prior to the forma- 

 tion of the tooth-sac, that many giant-cells contain clear round or oval 

 holes of various sizes. The larger and more distinctly defined ones, 

 in the centre of which a debris resembling fatty particles is sometimes 

 to be detected, appear to be originated by a disintegration of minute 

 portions of the protoplasm of the giant-cell. From this the author 

 takes it as possible that the giant-cells, after having ceased to exer- 

 cise their destructive, i. e. absorbing function, become disintegrated. 

 Morison takes it also as probable that sec[uestra are separated from 

 living bone by means of giant-cells, for, on examining a fresh seques- 

 trum, from a case of necrosis of the tibia, there were found Howship's 

 lacimae covering all aspects of the sequestrum, and the blood and pus 

 around the preparation containing multinuclear giant-cells floating 

 about. 



As regards the origin of giant-cells, Morison agrees with Kolliker 

 and others that many of them are in genetical connection with the 

 osteoblasts, but that others probably develop from embryonic con- 

 nective tissue ; for there occur bone spaces with here and there a giant- 

 cell entirely destitute of osteoblasts, but containing the nuclei of 

 embryonic connective tissue. These nuclei, generally scattered, are 

 here and there closely aggregated and show an interuuclear opacity, 

 which, however, has not the distinctly granular appearance of the 

 opaque cell-substance of a fully developed giant-cell ; but this appear- 

 ance is in variable degree, even in fully formed cells. It is possible 

 that the aggregation of nuclei may be the first stage in the formation 

 of a giant -cell ; one has only to imagine that these nuclei prepare a 

 cell material each around itself, which, coalescing with that round its 

 neighboiirs, produces the multinuclear giant-cell. 



Morpliology of the Saprolegniei. — The ' American Naturalist,' June, 

 1874, says that this doubtful family, that seems now finally deposited 

 in the Algae, has considerable economic interest from the destructive 

 effects produced upon fish eggs in the hatching trays, supposed to be 

 caused by Achhja prolifera. The following summary is translated 



* ' Edinburgh Medical Journal ' for October, 1873. 



