OCR Text |
Show 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 Tables. 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 r.ize ; these I have found surprising in Proteus and Sieboldia ; and m y 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 comparative magnitude of the red corpuscles, and their aggregate proportion 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 observations', especially as regards the mean sizes of the blood-disks. |