ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 263 



C3) Cutting:, including- Embedding- and Microtomes. 



Injection Preparations of Petromyzon.* — B. Mozejko gives an 

 account of his methods. The living fish is divided in two by a cut 

 through the region of the abdomen. Most of the blood escapes through 

 the cut ends of the large vessels, and gentle pressure is used to expel as 

 much blood as possible. Cannula; with slightly enlarged extremities 

 are introduced into the aorta, and into one of the great veins. A broad 

 ligature is then placed near the cut surface, in order to keep the cannulas 

 in position. The ligature must not be employed in such a way as to 

 damage the tissues. By an injection into the aorta, so that the 

 material is forced through to the veins, a single-coloured injection of 

 the vascular system is effected. A two-colour preparation may be 

 obtained by first injecting the veins. When the material so injected 

 has solidified, the arteries may be injected. By means of another 

 modification, a three-colour injection, distinguishing arteries, veins, and 

 sinuses, may be obtained. After injection is complete, the preparations 

 are placed, without removing the ligatures, into a fixing fluid which 

 contains formalin. After fixation the ligatures are removed, and the 

 preparations preserved. Portions may be embedded in celloidin, and 

 serial sections cut. In previous communications, | particulars as to the 

 materials suitable for injection have been given. 



The author has combined these injections with the clearing methods 

 recommended by Lundvall, by means of which semi-transparent pre- 

 parations are obtained. In the application of this latter process to 

 Petromyzon Jtuviatilis, it is necessary to bleach the highly-resistant pig- 

 ment by means of prolonged application of free chlorine. This precludes 

 the use of carmine or ultramarine in the injection material. Faint 

 colours such as chrome- veil ow are the most suitable. 



Demonstrating Presence of Starch in a Leaf.! — 0. H. Latter 

 exposes the leaf to sunlight for some hours, then boils in water for a few 

 moments, and afterwards dissolves out the chlorophyll with methylated 

 spirit. The alcohol is removed by means of water, and then the leaf is 

 treated with iodine solution. The leaf is next immersed in benzol, 

 which dissolves out the iodine from all parts except the blue starch- 

 iodine compound. Hence the blue colour shows up plainly, being no 

 longer masked by the yellow-browns of the cellulose and protoplasm. 



Method of obtaining Sections of Urinary Calculi. § — S. G. Shattock, 

 in his communication on the microscopic structure of uric acid calculi, 

 gives the following account of the technique adopted. 



The method consists in rubbing away half of the calculus on a file 

 or on glass-paper, the final part of the grinding being carried out on a 

 wet hone. In some calculi the nucleus is so differentiated as to readily 

 allow of identification. This is, however, not always the case ; one has 

 to guard against the fallacy of mistaking the section of a zone around 

 the proper nucleus for the nucleus itself, since both will present an 



* Zeitschr. wiss. Mikrosk., xxvii. (1910) pp. 248-56. 



t See this Journal, 1910, p. 257 ; Zeitschr. wiss. Mikrosk., xxvi. (1909) pp. 

 353-77, and 382 ; 1910, pp. 542-7. t Knowledge, xxxiv. (1911) p. 59. 



§ Proc. Roy. Soc. Med., Pathol. Section, iv. (1911. pp. 111-12. t 



