1881.] 



MICEOSCOPICAL JOTJEJ^AL. 



69 



ping of the halves of the frustule 

 along the raphe is effected, it 

 may be most easily seen in some of 

 the coarser Pleurosigmas. In broken 

 shells of P. attenuatum and P. for- 

 ?nosum I have seen it very plainly 

 demonstrated. Sometimes the thick- 

 ened line of silex which borders one- 

 half of the frustule, will be found 

 sticking out alone, the thinner part 

 of the shell being broken away from 

 it. Sometimes it will be in its normal 

 position, but the lateral halves of the 

 shell will be separated by pressure so 

 as to show on one side the thick 

 edge, and on the other the fitting gut- 

 ter caused by the projection of a thin 

 lip. Occasionally also a cross frac- 

 ture of the shell will be found on a 

 broken fragment, in such position that 

 we get the benefit of a cross-section, 

 and see the whole joint in the form I 

 have described. 



Examination of Blood- 

 Tanner's Blood.* 



l)r. 



Under the microscope, blood ap- 

 pears as a colorless fluid, in which 

 float an indefinite number of circular 

 disks, of a pale yellowish color. 

 They assume very characteristic dis- 

 tortions in spreading and in drying, 

 being drawn in at one point into a 

 slight notch, or prolonged into a 

 small sharp prominence, or drawn 

 out into a distinct balloon shape ; 

 they are often changed by mutual 

 pressure in drying, so as to indent 

 each other, and, for this reason, 

 along the edge of a small clot they 

 assume an elongated form, pointing 

 toward the edge of the clot. When 

 dried upon glass, they can be easily 

 cut into fragments by drawing a knife 

 or needle-point through the spot, and 

 the fragments, if not quite dry, will 

 round themselves toward or into the 

 appearance of small but perfect disks. 

 I have seen disks which, in spreading 

 very carefully upon glass, for the 

 purpose of retaining their natural ap- 



. * Condensed abstract of a lecture delivered 

 by Dr. R. H. Ward, before the Troy Scien- 

 tific Association. 



pearance, had been torn apart into 

 sections which became round, and 

 would have been considered indepen- 

 dent disks, if a slight change of position 

 had separated them from each other 

 and mixed them with other disks. 

 When treated with various solutions, 

 with heat, electricity, or other dis- 

 turbing causes, they assume forms 

 that are indented, vacuolized, nucle- 

 ated, surrounded by knobs which 

 often separate into distinct globules, 

 or are resolved into a net work of 

 fine fibres. There is still some doubt 

 as to the exact relation between these 

 artificially produced appearances and 

 the original structure of the disk. 

 They become shrunken and shriv- 

 eled in long wasting diseases, and by 

 long abstinence from food. At the 

 close of Dr. Tanner's fast of forty 

 days, during which time it is beyond 

 question that he at least abstained 

 from any ordinary and adequate sup- 

 ply of food, the red corpuscles of his 

 blood were found to be extremely 

 shrunken, jagged and broken in ap- 

 pearance, and supplied with roughly 

 projecting points ; and, although the 

 character of his blood began to im- 

 prove immediately after the resump- 

 tion of an ordinary diet, it was more 

 than a week before all the disks were 

 found to present a normal appearance. 

 The disks may be soaked out almost 

 unchanged from a small dried clot or 

 stain, and may often be recognized in 

 the thin portions of the clot itself, if 

 it be cleared up by dissolving out the 

 coloring matter, and subsequently 

 staining the pale residue. These 

 disks are characteristic of blood, and 

 are positively recognizable by an ex- 

 perienced and competent person. It 

 would be gross incompetence to mis- 

 take, for them, starch or wood-disks, 

 about which doubt has been ex- 

 pressed. The real danger of error is 

 in regard to spores, which have been 

 mistaken for blood disks by persons 

 of ability ; but such a mistake ought 

 not to occur again ; since the danger 

 of it is well-known. 



The coloring matter of the blood 



