Memory

In so far as a person draws identity from storing his own past, memory provides much of the pattern of personality. The storage capacity of the brain, some 10,000 million interconnected brain cells, is so vast that there is room for high level of retention, but recall is another matter and what is, in fact, stored may prove elusive to recall. Readiness of recall is associated with use. What is not reinforced by use tends to recede from consciousness, but it can be relearned more rapidly than if it had never been learned, Things experienced together tend to be stored as an interrelated pattern so that the recall of a part may bring back the whole. The fact that recall depends on stimulating clues can lead to confusion because more than one memory store may be tapped by the same stimulus, leading to conflict. Recall may also be facilitated or blocked by emotional factors associated with the matter it is sought to remember.

The amount that we can remember at any one time, and subsequently retain, depends on the meaningfulness of what is learned. Meaningless material, like lists of nonsense syllables, is more slowly learned and more quickly forgotten than real words of relevant sentences. Memory can be deceptive in so far as past events may be disordered on recall. Some of what happened may be forgotten, and some things that did not happen may be unconsciously added. The capacity for memory is observable from the first days of a child's life, but memory matures slowly and events cannot be remembered over an extended period of time much before the age of three. For most people, the earliest memories extend back to the end of the second year of life.

In all these processes of memory, recognition is to be distinguished from deliberate recall. Some one unable to describe in detail an acquaintance made at a party a few days earlier may recognize him instantly if he meets him. How people remember varies considerably. Some make a great deal of use of visual memory; others remember with equal efficiency without visualization.

The physiological basis of memory has still to ' be elucidated. At one time it was thought that information was stored in the brain by the establishment of neural circuits within the immensely complicated network of neurons of which the brain is composed. But memory survives flushing the brain with electrical charges large enough to wipe out all traces of memory so laid down. It is now conjectured that memory is somehow imprinted in the substance of neurons and not only in the circuits set up in groups of neurons. Recent research has led to the hypothesis that there are two different memory stores; a short-term system in which incoming information may be held for a brief time (15-30 seconds) after which it is lost if it is not processed in some way, and a long term relatively permanent system. Just how information is selected from the short-term store for retention is not yet fully understood. It is assumed that short-term memory is based on electrical activity in the brain, but that long-term storage involves a more permanent change in the protein structure of neurons, a chemical Consolidation process by alternating protein molecules. Forgetting, where it is not simply a retrieval problem, seems to be due to biochemical neutralization of RNA by RN-ases. What happens when we call on available information (decoding) remains e to be explained. This model fits the facts quite well, including those that the retention of recent memories becomes more difficult with age and that certain drugs influence recall. How the brain selects what is to be retained presumably depends on the existing content of the brain. What fits into one or other of the association networks is more likely to be incorporated as a permanent a modification; what does not is more likely to be rejected.

Madras

The city extends along the coast north of the river Adyar, and is crossed by the meandering river Cooum. It has no well-defined urban structure and resembles a collection of sprawling suburbs, but industry is mainly in the north, residential suburbs in the south.

The climate in Madras is hot, with an average daily maximum throughout the year of over 84°F. (28°C.) and exceeding 100°F. (38°C.) in May and June. Night temperatures range between 67°F. (19°C.) in January and 82°F. (28°C.) in May. The lowest temperature ever recorded in Madras is 57°F. (14°C.). Rainfall averages 50 inches in the year, of which over half falls in October and November, whereas January through April accounts for less than four inches.

Madras grew from a British settlement of 1639 in the village of Madraspatam, protected by Fort St George, and became the principal British factory on the Coromandel coast. It eventually absorbed the surrounding towns of Adyar, Sembiyam, Saidapet, and St Thomas Mount, which are now suburbs. It is a centre of the leather trade and has two very large cotton mills. There are also manufactures of aluminium goods, clothing, tobacco, and matches.

Instrument used for measuring the pressure of gases. The simplest type of manometer is an open- ended U-shaped tube, filled with mercury or other liquid which lies in the bend of the tube and rises a short way up each arm. The gas is connected to the end of one arm while the other end is left open. The liquid is thus subjected to pressure from the gas in one arm and to atmospheric pressure in the other. When the gas pressure exceeds the pressure of the atmosphere, the liquid rises in the open-ended arm. The difference between the heights of the liquid in the two arms is measured, and its weight calculated. This weight is then added to the known atmospheric pressure. The sum is the pressure of the gas. Such pressure is often expressed as the height of the liquid in the tube. Normal atmospheric pressure at sea level, for example, is 30 inches or 76 cm of mercury.