The science of life : fully illustrated in tone and line and including many diagrams

BOOK 1

@iEVACP WeEDRE 2

THE COMPLEX BODY-MACHINE AND HOW IT WORKS

§ 1. What Every Schoolboy Knows about the Body. § 3. Blood. § 4. The Course of the Blood. § 5. Breathing.

Lives within our Life.

§ 6. Kidneys and other Exhaust Organs.

§ 2. About Cells ; the Lesser 7. How our Food becomes Blood.

§ 8. The Continual Struggle against Infection and Chill.

§ 1 What Every Schoolboy Knows about the Body

HE writer of a general review of the

sciences that concern life such as this we are engaged upon is confronted by certain peculiar difficulties. He is writing for readers nearly all of whom have some knowledge of the subject in hand. He is threatened, therefore, on one hand by the probability that he is boring his readers with what they know already, and on the other by the probability that he is assuming they know too much. The writer of the text-book or the university lecturer is free from these perplexities. His readers and hearers are under compulsion to go on attending. He can say everything. He can inform his victims, graciously and elaborately, where their backbones are to be found and impart the stirring discovery that “‘ at the top of the spinal column we find the head, of which the larger part is the cranium or brain case, below which are two passages separated by a horizontal partition, the upper one being the nasal passage and the lower the mouth.” And he can go on in that strain for as long as he likes and then jump into technicalities that will make our heads spin.

We cannot do that sort of thing with that much magnificence here. Yet our betterinformed readers must allow us to run through, as compactly as possible, a certain amount of knowledge they no doubt acquired at school. If these better-informed readers will run beside us, they may find a fact or two of interest for themselves on the way and arrive at our more detailed expositions with their own knowledge sharpened and refreshed. Anyhow, it has to be done. We are going to recite here what, in Lord Macaulay’s phrase, “every schoolboy ” knows about the body.

We will assume that the reader is already aware that practically every movement of the man and mouse we described in the First Chapter is caused by muscles and that

24

he knows these muscles are the meat or flesh that clothes our skeleton. We will assume, too, that he knows the general structure of his skeleton. He knows where to find his backbone, the tie-beam of all his bony framework. He knows it is composed of separate bones (the vertebra) jointed together to make it flexible, while at the same time the nature of the joints and the strong ligaments binding it together limit this flexibility and make it rigid enough for its supporting and strengthening function. It encloses and protects a vitally important nervous organ, the spinal cord. The column is hollow, a flexible tube; each vertebra has the shape of an irregular knobbly ring, and when they are all jointed together the holes in the rings form a smooth, continuous canal in which this spinal cord is securely housed. Above the canal opens into the brain-case and through this opening the spinal cord is continuous with the brain. All this is matter of common knowledge, and so, too, is the fact that the joint-surfaces where two bones have to slide over each other are covered with thin layers of grisile, as smooth as glass. Moreover, the joints are enclosed in close-fitting bags which contain a watery fluid to lubricate the sliding bones. At the joints the bones are lashed together by strong white fibrous bands, or ligaments. These jointed bones are worked by the muscles, which are the “ flesh” or “meat? of the animal. Muscles and bones form nearly all the substance of the limbs of mice and men. Muscles are generally band- or spindle-shaped, and they are joined usually at the ends to two separate bones, which they pull together by altering their shape. They have the power of becoming thicker and shorter. No doubt the reader has amused himself by watching his “ biceps ” muscle thicken up as he bends and tightens his arm. Except for the inside of the skull, chest, and belly (abdomen is merely a polite word for the latter) we are all bone and muscle. The human arm