------------------------------------------------------------- Total number | Young | Ripe | Old | corpuscles | corpuscles | corpuscles ------------------------------------------------------------- Arterial blood 15000| 1950 (13%) | 840 (5.6%) | 12210 (81%) Venous " 16400| 656 (4.0%)| 2788 (17.0%)| 12956 (79.0%)
The argument based on figures such as these assumes that the function of the bone-marrow is =continuous=; an assumption which Uskoff indeed seems to make.
But if the bone-marrow is constantly absorbing the lymphocytes to such an extent, it is quite incomprehensible how the normal condition of the blood can be preserved, bearing in mind the extent of the bone-marrow and the rate of the circulation. All evidence indeed tends to shew that on the contrary the bone-marrow performs its functions discontinuously, inasmuch as elements continually grow to maturity in the bone-marrow, as we have above explained, but they only emigrate at certain times as the result of chemical stimuli. It is obvious _à priori_ from this consideration how inconclusive must be the results of experiments such as these of Roietzky[17].
Far more important for the elucidation of the function of the bone-marrow are =clinical observations= on cases in which considerable portions of the bone-marrow are replaced by tissue of another kind. We may best divide the observations on this point into two groups: 1. malignant tumours of the bone-marrow, 2. the so-called acute leukæmia.
There are unfortunately very few available observations as yet upon the first group. Still rarer are the cases in which as is necessary the whole bone-marrow has been subjected to an exhaustive examination, which alone affords adequate evidence of the extent of the defect.
Amongst the changes of the bone-marrow arising from tumours one may distinguish two groups, according to the nature of the condition of the blood. The first type is exemplified by a case of Nothnagel published in his work on lymphadenia ossium. Here during life the blood shewed, in the main, the features of a simple severe anæmia; but in addition isolated normoblasts, small marrow cells, and moderate leucocytosis. The autopsy, at which the whole skeletal system was subjected systematically to an exact examination, shewed a complete atrophy of the bone-marrow, and replacement of the same by the tumour masses. In this case then the condition of the blood _in vivo_ is satisfactorily explained by the absence of function of bone-marrow. Nothnagel conjectured that the formation of the scanty nucleated red blood corpuscles occurred vicariously in the spleen, that of the leucocytes in the lymph glands.