1875. | RED BLOOD-CORPUSCLES. 477 
on the contrary, are generally somewhat contracted by similar drying. 
The complete and permanent preservation of their form by drying 
seems to be a characteristic of the red blood-corpuscles ; other soft 
bodies, such as lymph-corpuscles or pale blood-globules, lose their 
shape, however carefully dried. Of both kinds of the red corpuscles 
I have many specimens thus prepared more than a third of a century 
since, and they are still as beautifully perfect as ever, though they 
are naked, as at first, on the glass slides, protected only by wrapping 
paper, and have often travelled about, with military baggage and 
otherwise, both by sea and land. The blood prepared in this simple 
manner only requires to be kept dry. And thus it would be easy 
for voyagers to preserve and bring home specimens of red blood- 
corpuscles quite suitable for mensuration. 
Special circumstances, too, of which we have not yet sufficient 
knowledge, may affect the value of any series of such measurements 
as those recorded in these T'ables. When a bird is much excited, 
and the circulation quickened by attempts at its capture in an aviary, 
the oval figure of its red blood-corpuscles may be more elongated 
than in the same bird when quietly at rest. In Batrachians and 
Reptiles the corpuscles are so large as easily to admit of a perception 
of variations in their size; these I have found surprising in Proteus 
and Steboldia; and my attention was sometimes arrested by like 
diversities in other Vertebrates at different times or seasons, though 
not in so many observations and with such notes as would be needful 
for satisfactory conclusions. But the facts are sufficient to show that 
exact and extensive investigations are yet necessary on the compa- 
rative magnitude of the red corpuscles, and their aggregate propor- 
tion to the other parts of the blood, in one and the same animal at 
different seasons and under various circumstances :—for example, 
whether minute diversities in the corpuscles may not be found in 
man at the tropics and frigid zone; in animals at rest and during 
violent exertion ; in hibernating animals during winter and summer ; 
in species subject to periodic increase of temperature, as observed by 
Dr. Sclater in the Python during incubation (Proc. Zool. Soc. 1862, 
p. 365, and 1870, p. 97); in males and females; in the arterial and 
venous systems, and in their different parts; also in relation to the 
ever-varying state of the liquor sanguinis. Such delicate inquiries, 
indeed, would require much care and labour, but might be rewarded 
with valuable results. Pathological or septic changes are out of the 
present question ; but to it belongs the fact that in a single healthy 
species the corpuscles are so prone to minute variations of size that 
of these no two observers, or even one observer, can be certain of 
obtaining precisely the same average measurements. 
No wonder, then, that those obtained by such an excellent micro- 
grapher as Dr. J. J. Woodward (Month. Micros. Journ., Feb. 1875) 
should not exactly agree with the results recorded by other observers. 
Nor need errors be suspected in measurements which differ little more 
than the objects measured, and which differences, though limited in 
degree, are sufficient to prevent an exact concordance in divers obser- 
vations, especially as regards the mean sizes of the blood-disks. 
