| OCR Text |
Show 478 PROF. G. GULLIVER O N [June 15, Considering therefore all the fore-mentioned disturbing circumstances, perfect agreement and precision in measurements of the corpuscles, and deductions of completely unexceptional averages therefrom, by various observers, or even by one observer, will appear hopeless. According^*, as already hinted, m y Tables cannot pretend to absolute exactness, and are only offered for what they may be worth ; and in the estimation of their value, allowance should be made for errors, whether instrumental or personal, more or less inevitable, notwithstanding the greatest care, in observations so extensive. But the relative value of the measurements, though probably not unexceptionable, may be entitled to more confidence as fair approximations to the truth. They were all made by me, under the same conditions and by the same means as described in former papers ; and by any valid micrometry, in spite of little mistakes or of variations in the dimensions of the corpuscles of this or that species, the comparative results will appear sufficiently uniform. Thus, if we compare the red blood-corpuscles of species of one order or family, e.g. Tragules and other Ruminants, the corpuscles in the former animals will constantly prove the smallest-so, too, in Paradoxurus and Canis, in Hippopotamus and Elephas, in Mus and Hydrochcerus, in Dasypus villosus and Orycleropus capensis, in Bhea americana and Casuarius javanicus, in Zootica vivipara and Anguis fragilis, in Bufo viridis and Bufo vulgaris, in Osmerus eperlanus and Salmo salar. And in like manner the facts are equally clear iii a comparison of the different orders ; so that the corpuscles are smaller in Ruminantia than in Rodentia, in Marsupiata than in Edentata, in Granivorse than in Rapaces, in Anura than in Urodela, in Sturiones than in Plagiostomi. PYREN^EMATOUS VERTEBRATES. In every animal, without any known exception, of this great division the red blood-corpuscle is characterized by the presence of a nucleus, which is plainly demonstrable in the majority of the corpuscles when examined on the object-plate under the microscope. Nor is the tax-onomic value of this fact at all affected by the old and still vexed question, as to whether the nucleus exists distinctly or at all in the corpuscle while it circulates within the living blood-vessels, or is formed only after its exposure to the atmosphere or chemical reagents. Many years ago De Blainville, Valentin, Henle, and others, and more recently Savory, supported the latter view ; and the former was adopted by Mayer and Kolliker, to which Brunke has lately conformed. The subject cannot be entertained here ; only it may be noted that I have satisfied myself of the substantial accuracy of Mr. Savory's observations on the blood-disks of some British Batrachians, but not of the validity of his conclusion therefrom, and that I have plainly seen in certain fishes the projections on the corpuscles, indicative of a nucleus, while they were flowing within the living blood-vessels. In Pyrenrjemata the thickness of each of the red blood-corpuscles is commonly about one third of its short diameter; they are oval, |
