index for comparing crania. In America Sam-
uel G. Morton Ijecame widely known by his great
collection of crania, now in the Academy of Nat-
ural Sciences in Philadelphia. His Crania Amer-
icana and Crania .^gyptiaca were important con-
tributions. His collections were, in 18.56, de-
scribed and commented on by another anatomist,
J. Aitken Meigs, who did much to establish the
modern methods of the mensuration of the skull.
No account of this period is complete without
a reference to the work of Jeffries WjTuan, of
Harvard University, who was a man of great
erudition and philosophical insight. As a mor-
phologist he had no superior among the anato-
mists of his day. He was the first to describe
the arrangement of the bou}' spiculoe in the neck
of the human femur, and to contrast it with
that in those animals that do not assume the
erect posture. He gave the first scientific de-
scription of the anatomy of the gorilla, and
wrote on symmetry and homology in the limbs,
on the vertebral theory of the skull, on terato-
logical subjects, on spontaneous generation, and
on the anatomy of the Hottentot. The question
of the unity or diversity of origin of the human
race, which was closely connected with the
origin of species, excited considerable attention
in America about the middle of the nineteenth
century. J. C. Nott and George R. Gliddon
were the Joint auth.ors of two important works
on this subject, entitled Types of Manlcind and
Inilificnou.i Races of the Earth. This study was
greatly stimulated by the discovery of human
remains in strata belonging to previous geologic
epochs, particularly at Engis and Spy in Belgium, Neanderthal near Diisseldorf, at many places in France, and in South America. Finally the prediction of Morton, made forty years before, was verified by Dubois, who found, in the Eocene strata of Java, fossil remains of a
remarkable transition form between apes and man (1S90-95). This department of anatomy was greatly advanced by the zeal and energy of Paul Broca (1824-80) of Paris, who systematized the methods in vogue, and invented many
new ones for the examination of the human body.
The localization of all active properties in the cells gave renewed impetus to the study of the structure of those "elementary organisms." At first this structure was believed to be compara- tively simple, the protoplasm of which the living substance is composed being apparently a struc- tureless jelly having peculiar physical and chem- ical ]n'oiiertics. Further advances toward per- fecting the microscope and microscopic technique have shown this to be a mistake. That proto- plasm has definite structure is now agreed by all: the details of the structure are still in dis- pute. Eminent in this investigation were Carl Heitzmann of New York, Flemming of Kiel, and Biitschli of Heidelberg. The phenomena of indi- rect cell-division (kariiol'iiirsis) were first con- nectedly observed by Schneider in 1873, and have been especially investigated by Van Beneden, Boveri, Oscar Hertwig, and Rabl. The ulti- mate constitution of the cell received a great deal of attention. Niigeli, in 1884, framed an hypothesis that protoplasm is composed of cer- tain elementary units, termed micellw. whose combination produces its physical and vital properties much as a combination of molecules produces the physical properties of inorganic bodies. Similar, more widely developed theories were framed by De Vries, Hertwig, Weismann, and others. Weismann attempts to explain the phenomena of heredity by supposing that bodily characters are caused by architectural peculiari- ties inherent in the original generative cells. This is, therefore, a reappearance of the theory of preformation so prevalent during the eighteenth centui'V. Experiments by Hertwig appear to have disproved 'cisniann's views. Great activity in the investigation of the structure of cells still continues. In America, Wilson of New York and Whitman of Cliicago have made important contributions to our knowledge of this subject. Heitzmann, of New York, is well known for his attack upon the cell-theory as commonly taught, holding that the cells of the body are connected by minite threads of protoplasm; a theory that has recently been confirmed to a limited degree.
The great strides made in our general knowl- edge of structure during the nineteenth century can only be briefly mentioned. The structure and development of bone was elucidated by Goodsir, Purkinje. Sharpey, and Kolliker, the osteoblasts being discovered by Gegenbaur in 1S64. The mechanism and development of joints were studied l)y Braune of Leipzig, Sutton of London, Dwight of Boston, and Bernays of St. Louis. The minute anatomy of muscle is still under consideration, and has been investigated by Krause, Pianvier, Cohnheim, and many others : Humphrey and Huxley (q.v. ) in England and Gegenbaur in Germany have written on the gen- eral morphology of the muscular system, and Gruber, Theile, Testut, and Lcdouble have inves- tigated muscular anomalies. The structure of the capillary blood vessels was first correctly demonstrated by Treviranus in 1830. The blood platelets or hematoblasts were discovered by Max Schultze in 1865. The lymphatics were investigated by Kolliker, Ranvier, and Sappey.
In the nervous s_ystem the discoveries have been many and brilliant, completely revolutionizing previous notions of its structure. Gratiolet first showed the convolutionary pattern of the brain; Broca was the first to prove that certain motor faculties may be localized upon the cerebral cortex; a subject upon which extensive researches have been made by Fritsch and Hitzig, Ferrier and Horsley. Ehrenberg ol Berlin appears to have been the first to describe, in 1833, the large cells of the cerebral cortex and of the spinal cord. The axis cylinder process of nerve cells was discovered by Wagner of Gottingen, Marshall Hall (q.v.) of London was the first to demonstrate reflex movements. Prochaska to discover the diff'erential function of the anterior and the posterior roots of the spinal nerves. By degeneration experiments instituted by Waller, by noting the myelination of nerve filu'es as done by Flechsig. and by comparative studies it became possible to trace in the central nervous system the paths by which sensations are received and motor influences discharged.
Improvements in technical methods finally made it possible to trace the processes of nerve cells to their iiMnutest ramifications. This gave rise to the neurone theory, which holds that the nervous tissue is composed of independent cells or neurones that may ramify extensively, some of the ramifications passing into nerve fibres and forming their active conducting elements. This theory has been applied with success to explain the architecture of the nervous system; a subject that is widely engrossing the
