SELECTED NOTES. 187 



Fig. 4. — Ventral surface of imago. 



,, 5. — Spiracle. 



„ 6. — Hair from Coronet. 



Plate XI. 



Fig. 1. — Peronospora infestans. g., Gonidia in situ on ends of mycelia 

 projecting from stoma of leaf. (After Cooke.) 



,, 2. — z., Zoogonidia penetrating epidermis of Potato stem (after 

 De Bary). 



,, 3. — Spores of Peronospora infestans, as seen on slide. 



,, 4. — Cytopus candidns. Branch of Mycelium with haustoria (h.), 

 penetrating between parenchymatous cells. 



,, 5. — o.g., Oogonium ; os., Oosphere ; aii., Antheridium in Cytopus 

 candidus (after De Bary). 



,, 6. — Mycelium (m.) with young oogonium (o.g.). 



flDicroecopical ^ecbnique. 



Preparation of Frozen Sections by means of Methyl and 

 Ethyl Chloride.*— In September, 1895, while watching Dr. John 

 B. Deaver perform a minor surgical operation with ethyl chloride, 

 the thought occurred to rae that this re-agent might profitably be 

 employed in preparing frozen sections for histological purposes. 

 The results thus far obtained have been exceedingly satisfactory, 

 and, while the method is somewhat expensive, no accessory appa- 

 ratus is required for the microtome. 



Hamilton's method of preparing the tissues for freezing gives 

 good results ( Text- Book Pathology, by D. J. Hamilton, Vol. I., 

 p. 58). Another way of getting the tissue ready is that recently 

 advised by J. Orth (Berlin klin. Woch., No. 13, 1896). One 

 hundred parts of Midler's fluid are mixed when wanted with ccn 

 parts of formol. Small pieces of the tissue under examination are 

 fixed and hardened in this solution in the incubator for three 

 hours. At the end of this time they are removed and thoroughly 

 washed, and alcohol is gradually added until they are placed in 95 

 per cent, alcohol. This latter re-agent must, of course, be removed 

 before the tissue is frozen. If desired, after washing, the specimen 

 may be at once transferred to the solution of acacia and sugar and 

 *From International Medical Magazine, Dec, 1896, pp. 706 — 7. 



