A manual of anatomy . n systems are absent. This varietyis found in the ends of the marrow-cavity of the long bones, formsthe bulk of the extremities of these bones and of the flat, short andirregular bones. This variety imparts lightness and permits of anincrease in size without sacrificing strength. The medullary, or marrow-cavity, is long, narrow and contains themarrow; it is found in the shafts of the long bones. It is lined by 20 OSTEOLOGY the endosteum which serves as an internal periosteum and a coveringfor the marrow. Bone Marrow.—In the adult there are two varieties of bone marrow,red
A manual of anatomy . n systems are absent. This varietyis found in the ends of the marrow-cavity of the long bones, formsthe bulk of the extremities of these bones and of the flat, short andirregular bones. This variety imparts lightness and permits of anincrease in size without sacrificing strength. The medullary, or marrow-cavity, is long, narrow and contains themarrow; it is found in the shafts of the long bones. It is lined by 20 OSTEOLOGY the endosteum which serves as an internal periosteum and a coveringfor the marrow. Bone Marrow.—In the adult there are two varieties of bone marrow,red and yellow. In early life only red marrow is found. The redmarrow consists of a delicate network of reticulum connected withthe endosteum. It supports various cellular elements and blood-vessels, nerves and lymphatics. The cellular elements are as follows: I. Myelocytes are large, nucleated masses of granular protoplasmthat exhibit ameboid movements. These are seen only in marrowunder normal conditions. ^.^v *..-i^. 9 m Fig. 2.—Blood. Elements of the bone-marrow of a mouse. X 700. (Sobotta andTluber, Atlas of Human Histology.) The preparation was taken from the femur of a full-grown mouse. I. Polynuclear giant-cell (); 2-7, marrow-cells; 2, marrow-cellwith annular nucleus (goes through the nuclear stage of 4 into that of 3—that is, into theordinary polymorphonuclear cell); 4 and s. acidophile cells; 6 and 7, mitoses; 8, ordinary ery-throcyte; 9 and io» nucleated erytnrocytes. 2. Erythrohlasls are nucleated red blood cells and are very numer-ous as the red marrow is practically the only tissue in which theyare formed. 3. Erythrocytes are normal red blood cells that have just beenformed from the preceding and are ready to go into the blood stream. 4. Leukocytes are white blood cells and are of the finely andcoarsely granular eosinophilic and basophilic types. 5. , or osteoclasts, are large, irregular masses of proto-plasm that may contain one or more
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Keywords: ., bookcentury1900, bookdecade1910, booksubjecthumananatomy, bookyea
