1907.] Fatty Degeneration of the Blood, 429 



Without entering into the chemical question as to the source of the fat 

 in fatty degeneration, how far, i.e., it is due to a transformation of the proteid 

 of the cell (as once held), and how far to the accumulation of fat 

 reaching the cell from without and appearing in it because not utilised, the 

 cardinal difference between the two processes remains, even though the 

 source of the fat should be the same in both. 



In the one case the fat accumulates or is stored in a cell of which the 

 cytoplasm is uninjured ; in the other it appears for the reason that the latter 

 is damaged and rendered incapable of utilising the fat which reaches it. 



With the fat that is not free, but combined, in the cell, neither term 

 deals; the presence of this is not recognisable, either by its microphysical 

 or microchemical properties. 



Technique. 



At the outset it is obviously essential to exclude the use of fat solvents, 

 like absolute alcohol and ether, as fixing reagents, and essential also that 

 the blood should not be dried. One preliminary method we tried was the 

 use of blood clot, but it proved less satisfactory than that of making films. 



Microscopic sections are readily cut from cylinders of blood that has been 

 received into, and allowed to clot in, narrow tubes, the clot being afterwards 

 fixed in salt-formol followed by 80-per-cent. alcohol. Such sections can 

 be stained for fat like those of other tissues. The method, again, of using 

 washed corpuscles (i.e., corpuscles washed in salt solution after having been 

 separated by the centrifuge from blood in which clotting has been prevented 

 by the addition of citrate of sodium) offers no special advantages, and after 

 making a trial of it we did not adopt it. 



The method finally chosen was that of making films on slides and cover 

 glasses. The film from first to last must be kept moist, and treated, in 

 short, throughout as a section of any tissue which is to be studied for the 

 presence of fat. The reason for this will be obvious, for any fat in the 

 leucocytes would, in the dried film, tend to transude, and become lost by 

 diffusion in the surrounding area. 



The film having been made on the slide in the usual manner, by drawing 

 a second slide in front of the blood, the slide is immediately placed with the 

 film downwards in a specially devised chamber of formol vapour. 



The chamber we use is a deep, oblong glass with a ground edge, and is 

 itself hardly larger in sectional area than an ordinary microscopic slide. 

 This is packed nearly to the top with cotton wool thoroughly soaked with 

 formol (40 per cent.), and on the top of the wet wool is laid a grating of 

 perforated zinc, near either end of which is soldered a cross strip of zinc 



2 I 2 



