A text book of physiology / by M. Foster.

  • Michael Foster
Date:
1880
Catalogue details

Licence: Public Domain Mark

Credit: A text book of physiology / by M. Foster. Source: Wellcome Collection.

Provider: This material has been provided by The University of Leeds Library. The original may be consulted at The University of Leeds Library.

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    determinate courses for the regulation of the energy of distant spots In other words, part of the irritable tissues must be specially arranged to form a coordinating nervous system. Still further complications have yet to be considered. In the lite of a minute homogeneous amceba, possessing no special form or struc- ture there is little scope for purely mechanical operations. As how- ever we trace out the gradual development of the more complex animal forms, we see coming forward into greater and greater pro- minence the arrangement of the tissues in definite ways to secure mechanical ends. Thus the entire body acquires particular shapes, and parts of the body are built up into mechanisms, the actions of which are to the advantage of the individual. Into the composi- tion of these mechanisms or 'organs' the active fundamental tissues as well as the passive or indifferent tissues, enter; and the working of each mechanism, the function of each organ, is dependent partly on the mechanical conditions offered by the passive elements, partly on the activity of the active elements. The vascular mechanism, of which we have just spoken, is such a mechanism. Similarly the urgent necessity for the access of oxygen to all parts of the body, has given rise to a complicated respiratory mechanism; and the needs of copious alimentation, to an alimentary or digestive me- chanism. . Further, inasmuch as muscular movement is one ot the cinel ends, or the most important means to the chief ends, of animal life, we find the animal body abounding in motor mechanisms, in which the prime mover is muscular contraction, while the machinery is sup- plied by complicated arrangements of muscles with such indifferent tissues as bone, cartilage, and tendon. In fact, the greater part of the animal body is a collection of muscular machines, some serving for locomotion, others for special manoeuvres of particular members and parts, others as an assistance to the senses, and yet others for the production of voice, and in man, of speech. Lastly, the simple automatism of the amoeba, with its simple responses to external stimuli, is replaced in the higher animals by an exceedingly complex volition affected in multitudinous ways by influences from the world without; and there is a correspondingly complex central nervous system. And here we meet with a new form of differentiation unknown elsewhere. While the contractility of the amcebal protoplasm differs but slightly from the contractility of the vertebrate striated muscle, there is an enormous difference between the simple irritability of the amoeba and the complex action of the vertebrate nervous system. Excepting the nervous or irritable tissues, the fundamental tissues have in all animals the same properties, being, it is true, more acute and perfect in one than in another, but remaining fundamentally the same. The elementary muscular fibre of a mammal is a mass of but slightly differentiated protoplasm, forming a whole physiologically continuous, and in no way constituting a mechanism. Each fibre
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