MICROSCOPICAL lAAMINATION. 73 







regulation size, namely, 25 mm x 75 mm, and cover glasses are re- 

 quired. The round form covers of 18 mm diameter (J-inch) and 

 0.17 mm to 0.25 mm in thickness were preferred, because they are less 

 easily broken in cleaning limn the square ones. Scalpels, tearing 

 needles, and a small alcohol lamp or a gas microburner are also 

 needed. 



The most important reagents used are as follows : Distilled water, 

 alcohol, dilute glycerin (glycerin water 1:1), iodin in potassium 

 iodid solution, dilute hydrochloric acid (strong acid and water 1:2), 

 and chloral hydrate solution (chloral hydrate crystals 8 parts, water 

 5 parts). 



As a clearing agent chloral hydrate was used almost exclusively, 

 and for all except the very densest brown or black seed coats it is 

 perfectly satisfactory, while even with the darkest colored seeds it 

 can be used with fairly good results if the heating is sufficiently pro- 

 longed. To make use of the reagent a portion of the sample is placed 

 'on a slide with a few drops of the chloral hydrate solution and heated 

 to boiling for a few moments. This dissolves the starch and has a 

 general clearing action so that the structure can be more clearly 

 seen. If the solution boils away befqre the clearing is completed 

 more should be added, as the specimen should not be allowed to 

 become dry during the process. With very refractory specimens a 

 small amount of nitric acid is sometimes added, but this reagent must 

 be used with care since it attacks the tissues so vigorously. Some 

 workers recommend caustic alkali, but this requires some little time 

 to act, and Javelle water (chlorinated potash) is open to the same 

 objection. 



LIST OF MATERIALS THAT MAY BE PRESENT IN CATTLE FOODS. 



It is not intended at this time to go extensively into the histologi- 

 car features of the constituents of stock foods. In the following list 

 are given the materials which have been reported in stock foods, 

 more or less frequently, by various observers." 



CEREAL PRODUCTS. 



The most important constituents in the list are the cereal grains, 

 such as wheat, barley, rye, corn, oats, rice, and their by-products 

 from milling processes. 



"Street, Report of New Jersey Agricultural Experiment Station, 1905; Bui. No. 

 117, Inland Revenue Department, Ottawa, Canada; Winton, Microscopy of Vegetable 

 Foods; Maryland Agricultural College Quarterly, May, 1907; Tirsch and Oesterle, 

 Anatomischer Atlas der Pharmakognosie und Nahrungsmittelkunde, 1893-1900; 

 Conn. Exper. Stat. bulletins, especially No. 132. 



