An Introduction to Human Anatomy
VIEWS.
- Author:
William Turner, M.B.,
Professor of Anatomy in the University of Edinburgh. The work under our immediate consideration is well worth the atten- tion of all those interested in the study of anatomy; not only the student, but also the expert. Professor Turner has arranged the matter in a most concise and excellent manner, quite novel in its nature.
The term skeleton is considered, when used in a limited sense, to apply to the bones, and when used in a more philosophic sense, to com- prise not only the osseous skeleton, but the cartilage and fibrous membranes which complete the framework of the body. The skeleton not only of man, but of various vertebrates, is most carefully discussed. The animal skeleton is first considered, consisting of the spine, spinal column; and the formula given for the vertebra} is C7, DI2, L5, Coc4=33, being the number of bones found in man. The vertebra are described in a clear and comprehensive manner, as also the anatomy of the thorax and skull.
Professor Turner now passes on to consider the ” appendicular skeleton,” by which is meant the upper and lower extremities. Some valuable observations are given in Chapter II. on the articulatory and muscular systems, and these are illustrated by excellent woodcuts; and an admirable description is here given of the mechanism of inspiration and expiration.
In Chapter III. the various tissues and fluids of the body are both anatomically and physiologically discussed at length, and we would draw the reader’s special attention to this part of the work, as deserving of the greatest praise for the general arrangement and interest of its contents; and also to the beautiful woodcuts and drawings of micro- scopic structures, made by Dr W. M. Banks, Dr Ewart, and Mr. C. Berjean, from specimens prepared by Mr. A. B. Stirling, Professor Turner’s assistant.
In Chapter V. the nervous system is described, and to this part of this admirable work we would turn our special attention. The nervous system, we are told, consists of a number of organs, named respectively nerve-centres, nerves, and peripheral end-organs and ganglia. The peripheral end-organs are minute structures con- nected with the peripheral extremities of the nerves, and are situated in the skin and other organs of sense, in the glands, blood-vessels, and muscles. Nerves are internuncial structures, being the means of com- munication between the different nerve-centres, or between nerve- centres and peripheral end-organs. When a nerve connects two nerve- centres together, it is inter-central; other nerves are called respectively centro-periplieral, periphero-central, motor, vaso-motor, secretory, trophic, inhibitory nerves of sensation, and of special sense, reflex, excito-motory, excito-secretory, excito-inhibitory, according to their respective functions; and in some fishes which possess electrical organs, nerves named electric exist. The structure of nervous tissue is now minutely described, consisting of nerve-fibres and nerve-cells. Medullated nerve-fibres are invested by a sheath of connective tissue, called the perineurium^ giving off processes passing into the nerve, and subdividing into fasciculi or funiculi. The perineurial connective tissue investing a fasciculi pre- sents, when treated with nitrate of silver, polygonal markings, which as Eanvier showed, are the outlines of a layer of flat endothelial-like cells. The fibres and fasciculi lie parallel to each other in the nerves but in the white matter of the brain and spinal cord the nerve-fibres are not arranged in such definite fasciculi as in a distributory nerve and the connective tissue between the fibres is the soft, delicate form,’ called neuroglia.
A medullated nerve-fibre, if examined immediately upon its removal from a living animal, as here described, consists of a soft, homogeneous, or glassy-looking substance, enclosed within a living membrane. If the same fibre be examined some time alter death, or after the addition of ether, acetic acid, collodion, &c., this homogeneous appearance disappears, and we see a delicate transparent membrane, the primitive-membrane, or neurilemma; also a delicate thread extending along the axis of the fibre, called the axial cylinder, or central band of Remah ; and a substance lying between these two membranes, called the white matter of Schwann, on the medullary sheath. An excellent diagram is here given of medullated nerve-fibres, showing the double contour.
Non-medullated nerve fibres are now described as characterised by the absence of a medullary sheath. The form of the fibre consists of pale grey, translucent flattened bands, the -g-^Vo” to -g^o of an inch in diameter, and are homogeneous or faintly granular. Nuclei are found in the substance of the fibre, and in relation with the primitive mem- brane. Nerve-cells, we are told, constitute an important division of nervous tissue, and are the characteristic structures in the nerve-centres, being susceptible to impressions or nervous impulses. The various nerve- cells are here fully described?the bipolar, pyriform,’and multipolar nerve-cells. Nerve fibres at their peripheral extremities terminate in connection with peculiar structures named end bodies, terminal bodies, or / eripheral end-organs, which are situated in the several organs of the body, the motor nerves ending in the voluntary and involuntary muscles, and the vaso-motor nerves in the muscular coat of the blood- vessels ; the sensory nerves end in the skin, mucous membranes, and organs of special sense ; the secretory nerves terminating in connection with the ultimate cell elements of the secretory glands.
After a careful and interesting description of the ramification of the nerves, and their microscopic appearance generally, the writer passes on to the descriptive anatomy of the cerebro-spinal nervous system, and we must direct special attention to the description of the development of the cerebro-spinal nervous axis. The membranes of the brain and spinal cord having been carefully described, the various plexuses of nerves are treated of, and the course of each individual nerve traced from its origin to its termination, in a short but concise manner. The brain is now minutely described, and this part of the work is illnstrated with beautiful woodcuts. Some interesting remarks are made relative to the weight of various brains of insane people, one male epileptic in which the brain weighed 64^ oz., another 62 oz. We are told that in the West Riding Asylum, out of 375 males examined, the weight of the brain in 30 cases was 55 oz. or upwards, and the highest weight was 61 oz. in a case of senile dementia, 60-g- oz. in a case of dementia, and 60 oz. in one of melancholia.
In the same asylum, out of 300 females examined, the weight of the brain in 26 cases was 50 oz. or upwards, the highest weights being 56 and 55 oz. in two cases of mania. The size and weight of the brain do not therefore, per se, give an exact method of estimating the intellectual power of the individual, and a high brain weight and great intellectual capacity are not necessarily correlated with each other. Professor Turner tells us if the adult human brain falls below 30 oz., that this low weight is not merely incompatible with intellectual power and activity, but is invariably associated with idiocy and imbecility, so that the human brain has a minimum weight, below which intellectual action is impossible. In the more cultivated races, we are told, the minimum weight limit of intelligence is higher than 30 oz. Theile records a case in the microcephalous idiot in which the brain only weighed 10’6 oz.; other similar cases are recorded as weighing 10 oz. 5 grs., and even 8-^ oz. Instances are on record in which the brains of idiots have exceeded even 50 oz. Dr Langdon Down observed the brain of a male idiot, aged 22, which weighed 59^ oz. In the West Hiding Asylum tables, the brain weights in 10 idiots were not less than 34 oz., and in 5 cases exceeded 40 oz. The average weight in the African races of the male brain is 45 6 oz., and of the female brain 42’7 oz.; in the Australian races it is 42*8 oz. for the male, and 39’2 oz. for the female ; in the Oceanic races the average weight of the male brain is 46*5 oz., and of the female 43 oz. Professor Turner draws the following conclusions from the above observations relative to the weight of the brain in the coloured races made by Barnard Davis : ” 1 st. That the average brain weight is considerably higher in the civilised European, than in the savage, races. 2nd. That the range of variation is much greater in the former than in the latter. 3rd. That there is an absence, almost complete, of specimens heavier than 54 oz. in the exotic races, so that the higher terms of the series are not represented. 4th. That though the male brains are heavier than the female, there is not the same amount of difference in the average brain weight between the two sexes in the uncultivated as in the cultivated people’s.”
The average weight of the adult human male brain is 49 to 50 oz., of the female 44 to 45 oz.; the male brain being 10 per cent, heavier than the female. The average weight of a newly born male infant is 11*67 oz., the female only 10 oz. The exact age at which the brain reaches its maximum size is by some authors stated to be from the 3rd to the 8th years, but it continues to increase in weight to 25 or even 40. After 60, the brain begins to diminish in weight to 45 oz. in the male, and 41 oz. in the female brain.
The cranial nerves are now accurately described and traced, and the anatomy of the sympathetic nervous system given, the volume con- cluding with a description of the various organs of sense. It is impos- sible to speak too highly of the arrangement of the matter contained in this work, which is clear and concise. It will become one of the leading works on anatomy, and we most highly commend it to the profession. Professor Turner is well known as the author of various works on anatomy; and as he is associated with Professor J, Humphry, F.R.S., of Cambridge, one of the greatest anatomists and surgeons of the age, as joint-editor of the Journal of Anatomy and Physiology, we have constant opportunities of perusing valuable articles on anatomy. The elaborate drawings throughout the work, executed by the gentlemen previously alluded to, are deserving of the highest praise.
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