594 



SCIENCE 



[N. S. Vol. XLVII. No. 1224 



tion of the magnesium sulphate is completed 

 by washing the crystals with very dilute al- 

 cohol, after which they may be immediately 

 used for further precipitation. 



In the complete paper the authors will dis- 

 cuss in some detail the application of this 

 method to the quantitative determination of 

 pectin in the laboratory or in co mm ercial jelly- 

 making establishments. It is considered es- 

 pecially desirable at this time to point out that 

 precipitation by magnesium sulphate may ad- 

 vantageously supplant the use of alcohol in 

 the household test for i>ectin. While alcohol 

 is not ordinarily available to the housewife, 

 Epsom salts are to be found in every home and 

 in almost every grocery store. By heating a 

 small quantity of the aqueous extract of fruit, 

 dissolving Epsom salts therein, and observing 

 the amount of pectin thrown out of solution, 

 one obtains an accurate measure of the pectin 

 content of the fruit and is thereby enabled to 

 form a judgment as to the amount of sugar 

 necessary to form a jelly. 



Discussion of many details of technique and 

 of certain applications of the method here 

 presented in outline are necessarily reserved 

 for presentation in the full paper immediately 

 forthcoming in the journal already named. 

 C. A. Magoon, 

 Joseph S. Caldwell 



Office Horticultukal and 

 PoMOLOGicAii Investigation, 

 BuEEAU OF Plant Industry, 

 Washington, D. C. 



the care and breeding of albino rats 



At this time when the government is using 

 great numbers of albino rats and mice for 

 inoculation purposes, mmierous letters have 

 been received from various sources asking for 

 information regarding a source of supply and 

 the care and breeding of these animals. This 

 demand is so widespread that it is deemed 

 most expedient to give this information in a 

 simple form and to disseminate it to the 

 greatest number of people by publishing it in 

 this journal. In so doing those persons who 

 are anxious to do their bit in this present 

 crisis and who reside sufficiently near base 



hospitals and cantonments may be able to rear 

 and supply these animals. 



Albino rats and mice are exceedingly easy 

 to raise. Their care and feed are practically 

 the same and the cages in which they are kept 

 can be identical. The cages for mice can, 

 however, be much smaller. Our colony at the 

 present time consists wholly of rats and the 

 following applies strictly to them. It in gen- 

 eral applies to mice also. These animals can 

 ordinarily be handled by the bare hands with- 

 out any danger of being bitten. Occasionally, 

 however, a mother with young may be less 

 docile if her young are disturbed. In such 

 cases the use of a pair of heavy gloves is ad- 

 visable. The oftener the rats are handled and 

 petted the less likely they are to bite. 



The cages in which our rats are kept and 

 which we have found most satisfactory are 

 made of one-fourth-inch galvanized wire net- 

 ting with all the corners, edges and doors 

 botmd, or reenforced by galvanized iron (Fig. 

 1). They are made 12 inches high, 18 inches 

 wide and 24 inches long. A partition of 

 woven galvanized wire, provided with a sliding 

 door (Z> 4in. X 4:in.), divides this into two 

 compartments 12 in. X 12 in. X 18 in- Each of 

 these compartments is provided with a woven 

 wire door (D, 6 in. X 6 in.) which slides up in 

 runners made of galvanized iron (_Bn). These 

 doors are of ample dimensions to enable one to 

 easily reach into all parts of the cage. 



The bottom is separate and comjKised of 

 galvanized iron 20 in. X 25 in. with three of 

 the sides turned up 1 in. The front side is 

 left flat to facilitate cleaning. The cage thus 

 sits in this bottom and can be readily lifted off 

 when cleaned. This process, which should be 

 attended to at least once in two weeks, can be 

 accomplished without handling the rats or 

 without danger of their leaving the compart- 

 ments to which they belong. This is done by 

 placing the whole cage on a broad table, lifting 

 the top about one half an inch and carrying it 

 along to the bare table. The rats are thus 

 forced along with the cage and the bottom left 

 free. The old sawdust and excelsior used for 

 bedding are now scraped out and a fresh sup- 

 ply added. The cage containing the rats in 



