PROGRESS OF MICROSCOPICAL SCIENCE. 35 



ditions under whicli red blood-corpuscles emigrate, and the question 

 arose whether the white blood- corpuscles leave the walls of the 

 vessels in the same manner, or whether they penetrate the epithelial 

 plates themselves. To decide this question, he examined the 

 mesentery, the tongue and the bladder of the rana temporaria and 

 the rana esculenta, and found that generally the white corpuscles 

 leave the vessels by means of stigmata. The irritation of the organs 

 was caused in different ways. Thus, the mesentery was exposed for 

 a few hours to the atmosphere, while the tongue was injured and 

 the bladder was injected by a weak solution of nitrate of silver. 

 Infusions of cinnabar into the blood wei-e also made with the view 

 to colour the white blood-corpuscles. Twenty-four hours after the 

 operation the animals were bled to death, and then the circulatory 

 system was injected from the aortic bulb by a solution of nitrate of 

 silver from 2 oVo ^'^ soVo- The examination of the preparation took 

 place immediately in a three-fourths i^er cent, solution of chloride 

 of soda, or after colouring with carmine in glycerine. The white 

 corpuscles could be observed in numerous phases of emigration. 

 The transmigration always took place at certain points (stigmata). 

 Had the process of emigration been stopj)ed in time, the emigrated 

 blood-corpuscles were to be seen in the sheath of vessels, or at a 

 shoi't distance from this. The form of the white corijuscles is 

 elongated in the state of escape. Many of them have prolonga- 

 tions, fixed in the stigmata. Sometimes numbers of white corjjuscles 

 accumulate on the outer wall of the vessels, so that the lining 

 epithelial membrane appears to be separated from the sheath of the 

 vessel. The author never observed that the plates themselves were 

 penetrated by the white corpuscles. As a result of the disturbance in 

 circulation, combined with the emigration of white blood-corpuscles, 

 it was found that the borders of the cells forming the vessels are not 

 so distinct as in a normal state. Between them are a greater number 

 of dark spots (stigmata) than in a normal state, generally not so large 

 that red blood-corpuscles could pass them. Dr. Arnold observed 

 that granules of cinnabar, as well as colloid substances, may leave the 

 vessels through the stigmata. The cause of the easier penetrability 

 of the vessels may be found in an alteration of the condition of the 

 cement connecting their cells. A great number of the emigrated 

 white corpuscles are carried off by the lymph-vessels. The author 

 thinks that with the disturbance in circulation during emigration 

 there are connected currents directed towards the walls of the vessels, 

 and that they are of different strength. 



The supposed Benal Organ in Crustacea. — Mr. A. S.Packard, jun., 

 in a recent paper says, that in dissecting the king crab one's atten- 

 tion is directed to a large and apparently important gland, conspicuous 

 from its bright red colour contrasting with the dark masses of the liver 

 and the yellowish ovary or greenish testes, and presenting the same 

 appearance in either sex. " The glands are bilaterally symmetrical, 

 one situated on each side of the stomach and beginning of the intes- 

 tine, and each entirely separate from its fellow. One of these glands 

 consists of a stolon-like mass, running along close to the great col- 



