## Metadata - Author: [[John Napier]] - Full Title: Hands - Category: #books ## Highlights - The late Professor F. Wood Jones called the human hand the "absolute bed-rock of mammalian primitiveness." He was referring particularly to the five-fingered state (pentadactyly). No mammal, reptile, amphibian or bird has ever evolved a form with more than five digits. There are many that have less, but none that have ever managed to scrape up an extra finger or two as a fixed characteristic of the species. ([Location 169](https://readwise.io/to_kindle?action=open&asin=B0089KLY5I&location=169)) - It only requires a little observation during periods of ennui while traveling in trains and on buses to conclude that the human hand comes in all sorts of shapes and sizes. The English language is rich in adjectives commonly applied to the appearance of the hand: from beautiful and elegant to powerful and cruel. To describe the texture of the skin we can choose coarse, velvety, smooth, hairy, horny, or moist. To describe its color we have the inevitable lily-white at one extreme and brick-red at the other. To describe function we tend to resort to "professional" analogies: a surgeon's hand, a musician's hand, an artist's hand, a navvy's hand. We also talk of handshakes as being vice-like, flabby, cool, friendly, or warm. ([Location 245](https://readwise.io/to_kindle?action=open&asin=B0089KLY5I&location=245)) - There are rogue cars that have to have engines replaced within the first few weeks of ownership, but there are no rogue hands. The skill of the hand lies in the brain and it is here that dexterity and adroitness (or clumsiness) originate. The hand is a mirror of the brain; therefore there can be no such combination as dextrous hands and clumsy brains. ([Location 260](https://readwise.io/to_kindle?action=open&asin=B0089KLY5I&location=260)) - The phalangeal index expresses the length of the three phalanges of the middle finger as a ratio of the total hand length. Functionally it reflects in primates the degree to which the hand is adapted for grasping and climbing in an arboreal milieu, or walking and running in a terrestrial one-the rationale being that the longer the fingers the greater is the capacity for grasping; and the shorter the fingers the more stable and powerful is the lever in quadrupedal ground-walkers.The human phalangeal index has a mean value of 49 percent. This figure is intermediate between that of ground-adapted monkeys such as the baboon, the patas monkey and the gelada (42-44 percent), and the arboreal specialists (52-58 percent).… ([Location 275](https://readwise.io/to_kindle?action=open&asin=B0089KLY5I&location=275)) - The hands of great apes are specialized in many ways but particularly in respect of their arm-swinging type of locomotion known as brachiation. Although they possess remarkably long fingers, the metacarpal and carpal sections are equally elongated, having kept pace with the fingers during evolutionary growth. Consequently the index value approaches 50 percent and is… ([Location 282](https://readwise.io/to_kindle?action=open&asin=B0089KLY5I&location=282)) - An interesting mechanism called double-locking occurs in orangutans. Owing to the exceptionally long palm, the tips of the fingers can be tucked into the skin-fold at the base where the finger meets the palm. With further flexion the locked fingers are rolled into the palm (Fig. 10), thus double-locking them. This mechanism is somewhat analogous to an engineer's over-center lock. The adaptive value of double-locking is apparent during feeding. While feeding, orangutans prefer to utilize the slender branches of the trees. They use their feet as well as their hands to distribute the weight evenly… ([Location 289](https://readwise.io/to_kindle?action=open&asin=B0089KLY5I&location=289)) - The power of the orangutan's grip by means of double-locking can be demonstrated with a piece of string. People cannot resist a direct pull along the length of the string, but orangutans have no such problem (Fig. 11). The moral here is… ([Location 294](https://readwise.io/to_kindle?action=open&asin=B0089KLY5I&location=294)) - The role of the skin in general terms has been epitomized in somewhat bluff, nontechnical language as the structure that "keeps the blood in, and the rain out." Never mind, the axiom, although crude, provides a starting point. Besides being water-and blood-proof, the skinbecomes thick where it is subjected to rough treatment, it is fastened down where it is most liable to be pulled off, it has friction ridges where it is most liable to slip. Even with our ingenious modern machinery, we cannot create a tough but highly elastic fabric that will withstand heat and cold, wet and drought, acid and alkali, microbic invasion and the wear and tear of three score years and ten yet effect its own repairs throughout and even… ([Location 300](https://readwise.io/to_kindle?action=open&asin=B0089KLY5I&location=300)) - The skin of the palm is firmly bound to the underlying, packing tissue of the hand. There arc areas, over the ball of the thumb and the "heel" of the hand, where the skin is relatively mobile. This is because the underlying fibrous tissue, which is heavily loaded with fat, forms a distinct pad. But elsewhere-as in the central… ([Location 305](https://readwise.io/to_kindle?action=open&asin=B0089KLY5I&location=305)) - There was a period during the early months of the last war when among naval gunnery personnel, severe flash burns of the palm of the hand were rather common. They were treated by a full-thickness skin graft (a full-thickness graft includes the fatty subcutaneous layer as well as the skin). The early postoperative results were encouraging. But when the patients started to use their hands again for grasping, the lack of the normal fixation offat to fibrous tissue in the center of the palm meant that the grip was slippery and ineffective, and objects thus gripped were flying about like orange… ([Location 307](https://readwise.io/to_kindle?action=open&asin=B0089KLY5I&location=307)) - When the starving internees of German concentration camps were finally freed in 1945, most of them had used up all their available stored fat, even from the walls of the heart. Yet in spite of the fact that the prisoners were little more than walking skeletons, their heel pads were intact, rounded, and as fatty as ever, and (although I don't recall any precise mention of this) I suspect that their hypothenar fat pads also survived. ([Location 438](https://readwise.io/to_kindle?action=open&asin=B0089KLY5I&location=438)) - In an incredibly small space, tendons, muscles, nerves, veins, and arteries arc packed as close as sardines in a tin. It is possible to wax quite lyrical over the functional effectiveness of the anatomical arrangements of the hand as Sir Charles Bell did: "and we must confess that it is in the human hand that we have the consummation of all perfection as an instrument." ([Location 441](https://readwise.io/to_kindle?action=open&asin=B0089KLY5I&location=441)) - The tendons of the short muscles of the hand (the interosseus and lumbrical muscles) join the assemble and play an extremely complex role in the mechanism of the hand. These short muscles are extremely well endowed with special nerve endings that provide them with a positional sense that has no equal elsewhere in the body. ([Location 484](https://readwise.io/to_kindle?action=open&asin=B0089KLY5I&location=484)) - The movement of the thumb underlies all the skilled procedures of which the hand is capable. The hand without a thumb is at worst, nothing but an animated fish-slice, and at best a pair of forceps whose points don't meet properly. Without the thumb, the hand is put back 60 million years in evolutionary terms to a stage when the thumb had no independent movement and was just another digit. One cannot emphasize enough the importance of finger-thumb opposition for human emergence from a relatively undistinguished primate background. ([Location 505](https://readwise.io/to_kindle?action=open&asin=B0089KLY5I&location=505))