ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



347 



Deceptive Results produced by Hardening Solutions.* — For 

 the diagnosis of keratin in animal tissues, Dr. H. Stcinbriigge has 

 applied Evvald and Kiibne's metbod to tbe investigation of tbe tissues 

 of tbe ear of mammalia for tbe presence of keratin as a normal con- 

 stituent, wbicb was a probability to be inferred from tbe morpbo- 

 logical relationsbip of tbe tissues to tbe ectoderm of tbe ovum. Tbe 

 sections were digested in a tryjjsin solution prepared in tbe usual 

 way from pancreas. Very divergent results were obtained in regard 

 to tbe degree of resistance to tbe action of tbis solution, wbicb was 

 tbe criterion adopted by Ewald and Kiibne for tbe presence of 

 keratin. Investigation sbowed tbat tbese divergencies corresponded 

 witb tbe degree of action of tbe hardening solutions employed in 

 preparing tbe tissues for cutting, and tbat tbe criterion in question is 

 worthless. 



Providence Microtome, f — Tbe original form of tbis microtome 

 was designed by Mr. N. N. Mason of Providence, E.I , U.S.A., and 

 was perfected by Rev. J. D. King. In its present form (fig. 71), it 



Fig. 71. 



:;iuiii^ 



is described by tbe Rev. A. B. H(i \ i il ps equalled by no 



microtome made, for extreme precision of movement and consequent 

 accuracy of performance in cutting sections. Witb a good knife in 

 good order, sections of 10 /jl to 25 /x thick can be made without 

 difficulty, and all alike." 



It consists of a heavy iron bed B, a knife-carrier A, and tbe 

 usual apparatus for holding and moving tbe object to be cut, g j. 

 The iron bed wbicb furnishes tbe clamj) h, and a solid support for 

 tbe knife-carrier and object-bolder, is 13-8 cm. long, 5-7 cm. wide, 

 and 6-8 cm. deep. Cemented to its top is a brass plate A, 6-5 mm. 

 thick. Rising through and above tbis is the cylindrical tube or 

 object-bolder y, 29 mm. in diameter. It projects 10 mm. above tbe 



* Zeitschr. f. Biol., xxi. (1885) pp. 631-5. 



t Bchrcna' 'Microscopo in Botany' (Amcr. ed. by Ilervcy and Ward), 8vo 

 Boston, 1885, pp. 188-'JU (1 tig). 



