82 PROPERTIES OF 



proach to the' nature of serum as not to be coagulated by 

 exposition to the air ; but it does not alter so considerably its 

 property of coagulating by heat, for the mixture with Glau- 

 ber's salts (in Experiment vn) coagulated at 125 ; and, I be- 

 lieve, would coagulate in a heat of 123, if long exposed to it; 

 whilst the pure coagulable lymph is fixed between 114 and 

 12O| (see Note xvi), and the serum not under 160 of 

 Fahrenheit's thermometer (see Note xvn). 



Of the white serum. 



Although the serum of human blood be naturally transpa- 

 rent, and a little yellowish, yet it is frequently found to have 

 the appearance of whey, and sometimes to have white streaks 

 swimming on its surface like a cream, and now and then to be 

 as white as milk, whilst the coagulum is as red as usual. In 

 all these three cases of .whiteness I have examined it in a 

 microscope with a pretty large magnifier, and have found it to 

 contain a number of very small globules, although naturally, 

 when transparent, no globules can be observed in 'it, notwith- 

 standing what has been affirmed by some authors. These glo- 

 bules differ from the red particles (improperly called globules) 

 in their size, which is much smaller ; and likewise in their 

 shape, which is spherical, whilst the red particles are flat. 

 They agree more with the globules of milk, I have compared 

 them with those of woman's milk, and have found that in the 

 milk the globules are of different sizes, some being three or 

 four times as large as others, and the smallest little more than 

 just visible, when viewed with a lens of one-twenty-third of an 

 inch focus, whilst those of the white serum are more regular, 

 and are all of them about the size of the smallest globules of 

 milk (LVII). Of this white serum I have met with the following 



(LVII.) This is an accurate account of the microscopical characters 

 of the milky matter. A few granules, about ^oVo of an inch in dia- 

 meter, are commonly mixed with it ; but its bulk is made up of particles 

 scarcely -5^075^ ^ an i ncn in diameter, and agreeing in all respects 

 with those which compose the molecular base of the chyle, a and give 

 to it the white colour. These are not to be confounded with the chyle- 

 globules, of which the average diameter is about -^VTJ of an inch. b 



a Appendix to Gerber's Anat. pp. 21,98, b See the Tables of Measurements, 

 figs. 274-8 ; and Dr. Willis's tr. of Wagner's Note cxviii*. 



Physiol. i, 247, fig. cxlix. 



