15. Monkeys and Fleas
The wingless parasites known as pediculi are not known as active agents in spreading disease germs, probably because they do not readily transfer themselves from one animal to another. It is in this connection a really remarkable fact that monkeys are not infested by fleas, and that only in few cases and not in many kinds have pediculi or acari been observed. In this respect the lower races of men (and even the higher) seem to have fallen away from a grade of excellence attained by their despised quadrumanous cousins. When this fact as to the freedom of monkeys from insect parasites is mentioned, those who have watched monkeys in captivity will immediately say, “Surely I have seen monkeys carefully picking insects from one another’s fur.” The fact is that it is this very habit of “picking” which prevents monkeys from harbouring fleas. Whereas a dog or a cat can only scratch, the monkey has an opposible thumb and delicately sensitive fingers. That which has become the hand of man, with all its marvellous skill and efficiency, has been elaborated in its early stages as a means for keeping the hair clean. When monkeys are seen carefully removing something with finger and thumb from their own or their companion’s hair, it is not an insect but a little piece of fatty secretion and scurf which is thus removed. The habit, which seems to be general in all kinds of monkeys, even with the anthropoids, such as the chimpanzee and the orang, has of course been efficient in removing any parasitic insects which may at one time have infested monkeys—all other furry animals are liberally supplied with them, as also are birds—but is now preventive of any re-establishment of such visitors. The popular judgment of the monkey’s habit is similar to that of the Japanese Aino, who remarked to a traveller who arranged to have a bath in his room every day that he must be a very dirty man to require it.
16. The Jigger Flea
One flea is recorded as having been once taken on an anthropoid ape (a gorilla), and is the “jigger,” Pulex penetrans. This is a very serious pest, the history of which shows how man himself opens up the path by which dangerous diseases spread. The jigger-flea was originally known only in the South American tropics. It spread from there to the West Indies in the last century. It burrows into the skin, usually between the toes, but elsewhere also, and causes an abscess and sore as big and deep as a hazel-nut. Several such cavities at a time are dangerous, and often lead to blood-poisoning and death. Europeans avoid the burrowing of the jigger by having their toes carefully examined every morning, but black men are less careful. From the West Indies, about thirty years ago, the jigger was carried in ships to West Africa. There it flourished and spread from village to village across Central Africa, decimating the population. It appears to have been carried to a large extent by dogs, in whose skin it flourishes. It has now passed through Africa to India, and we shall no doubt soon hear of its having completed the circuit of the globe.
A great many kinds of fleas are known, many furry animals having their own special species, which does not leave them to take up its dwelling on other kinds of animal. The common rat has a large flea of its own, which apparently is not the flea which carries the plague from rats to men. It is a “wandering” flea which does this, namely, the Cheops flea. This flea, common in the East but unknown in colder regions, does not stay as one could wish it to do—on the rat; but travels about visiting human beings and dogs, and so carries the plague bacillus from rats to men. In the absence of these fleas plague would be a rat-disease unknown in men. It is probable that we do not nowadays live so thoroughly cheek-by-jowl with rats in Western Europe as formerly, so that even if rats infected with plague and harbouring the Eastern Cheops flea arrive in our docks, the wandering flea is too far off to reach us in our modern houses.
17. Public Estimate of the Value of Science
The Royal Society, the full title of which is The Royal Society of London for the Promotion of Natural Knowledge, has its anniversary meeting and dinner on St. Andrew’s Day. The health of the medallists of the year 1907 was given from the chair by Lord Rayleigh, and they replied one by one to the toast. Professor Michelsen, of Chicago, received what is considered the greatest honour the society has to bestow—the Copley Medal (founded more than two hundred years ago) for his researches on light. He related in his speech how he had tried to interest a wealthy business man in the experiments going on in his laboratory, in the hope that his friend might be moved to give pecuniary aid for the provision of new apparatus. One by one, he showed his delicate instruments and explained their uses; no impression was produced. At last he explained how the bright lines of the spectrum of flame, coloured by incandescent elements (such as theatre-goers know as red fire, green fire, blue fire, &c.), can be recognised by means of the spectroscope in the light of the sun—proving the presence of the metals and other elements of this earth in that remote body. He especially explained and showed his friend the experiments by which sodium, the metal of which caustic soda is the “rust,” is thus proved to be present in the sun. At last his friend spoke. He said: “Who the —— cares if there is sodium in the sun?” Professor Michelsen did not tell the fellows of the Royal Society how he replied to that abrupt inquiry.
A more encouraging speech was that of Lord Fitzmaurice, the Under-Secretary of State for Foreign Affairs, who replied to the toast of the guests. He declared, in so many words, “It is every day becoming more and more certain that science is the master.” He said that in his own business as a diplomatist he found that the chief matters which he had to discuss and decide depended on scientific knowledge and the information and guidance given to him and his colleagues by scientific men. In the beginning of the eighteenth century the British Government had sent a bishop and a poet to negotiate the Treaty of Utrecht. But neither would be of any use in modern diplomacy. What they always had to seek at the present day was the aid of the scientific departments of the Navy or the Army, or of the Royal Society. Such matters as the relative merits of a Channel tunnel or a Channel ferry, the limitations of territory by land, by sea, or above the land in the air, the international agreements as to measures for checking the spread of disease or of insect pests, and, indeed, most matters which had come before him since he had been in office, had to be decided by the scientific experts. He did not propose that diplomatists should at once vacate their posts and endeavour to secure the occupation of them by men of science, but he thought that at no distant date such a course would be considered not only reasonable, but necessary!
18. The Common House-fly and Others
The common house-fly is not so innocent as he looks, but really a dirty little thing. He has not a sharp beak-like proboscis, and cannot stab, but he has a soft, dabbing proboscis, which he pushes on to every kind of filth as well as walking with his six legs on such matter. Then he comes and wipes off minute particles and germs on to our food, our lips, our fingers, and faces. It is quite certain that he, and others allied to him, are thus the means of spreading typhoid fever in camps where there are open latrines and open larders and mess tables. The house-fly breeds from a maggot, just as the blue-bottle or blow-fly does, but very few people have ever seen or recognised the maggot of the house-fly. The reason is that it lays its eggs in horse dung, and the grubs are hatched in the muck-heaps of stables. That is also the reason why it is much less numerous in London than it used to be, since stables and mews are now fewer and cleaner than they were. It is also the reason why the house-fly abounds in ill-kept country inns and farmhouses. Its breeding ground is just outside the window.