20 MEMORANDA. 



Now I am perfectly aware that tlie above appearance is 

 given by some authors as presenting itself under the micro- 

 scope^ but less distinguished writers make no mention of the 

 condition under which the yellow colour is observed, and 

 most elementary "text-books" of physiology for students 

 convey the idea that the coloured corpuscles are actually of a 

 faint yellow hue. 



Now it stands to reason that no amount of yelloiv discs can 

 produce the intense scarlet of human blood ; on the contrary, 

 I hold it as a positive fact that the colour of each particular 

 flattened, circular, or oval disc of mammifer, bird, reptile, 

 batrachian, or fish, is as deep and vivid as the mass of the 

 blood of which it is a constituent part. The scarlet disc of 

 man, when magnified by 500 diameters, fades almost to a 

 pale straw colour; for, as you know perfectly well, the 

 crimson that painted a surface the b -8 couth (about) of a 

 square line is difiused over a superficial extent of not less 

 than 2" 10 square lines, which is a chromatic dilution of 

 142'800 times. It is not, therefore, surprising that the 

 homoeopathic quantity of red in the amplified image, be- 

 sides loss, should hardly be recognised as such. 



Suppose fl5, 3'2, of fresh blood in a flat-bottomed glass 

 vessel, 1"5 inch wide (cylindrical) ; the mass will have 

 nearly the proportions of a blood disc, and a bright scarlet 

 hue. Imagine, now, the same blood in a similar vessel, 750 

 inches wide, and thinned out with transparent syrup, of the 

 specific gravity of the blood, until the mixed fluid would 

 stand 150 inches high in the glass; would not this liquor, 

 when viewed from above, give the same impression of colour 

 to the eye as a single blood-corpuscle as seen " under the 

 microscope," with a power of 500. 



I beg to say, that I believe the error just pointed out in 

 descriptions to exist only in the terms used, without care 

 being had to explain why the red corpuscles appear faintly 

 yellow ; but this inadvertence is calculated to mislead pro- 

 fessional men, and even some professors in this country, 

 who teach physiology entirely from books. — Christopher 

 Johnston, M.D., Baltimore, U.S. 



Use of the Microscope. — The following case is so interesting 

 a triumph for the microscope that I send it for your perusal, 

 and insertion, if you please, in the ' Journal.' 



A few days ago a medical friend told me of a patient who 

 was then ])assing very large quantities of fat in her evacua- 

 tions, and who had been doing so for a long time; he oftercd 



