3i6 



SCIENCE. 



[Vol. X. No. 256 



damaged. ' They who go down to the sea in ships' assume the 

 perils of the voyage, among which is this occurrence of finding 

 themselves on an infected vessel, and being compelled to undergo 

 a cleansing ; for they have no right to bring their perils ashore and 

 endanger others." The ship, with those on board, is held ten days 

 for observation, and then allowed to proceed to the upper station, 

 where she undergoes further treatment, and then goes to the city. 



The methods practised by Dr. Holt are very thorough, and in 

 their application, a tugboat, fitted up with all the necessary ma- 

 chinery, is employed. The bedding of the vessel, together with 

 cushions, mattresses, carpets, rugs, etc., is removed from the ship 

 to a commodious building in close proximity to the disinfecting 

 wharf, where they are treated by moist heat at a temperature of 

 not less than 230° F. During this process of steaming, every article is 

 perceived to be saturated and intensely hot, the steam freely pene- 

 trating to the interior of mattresses, double blankets, etc.; but so 

 great is the heat in the texture of the fabrics as to immediately 

 expel all moisture upon drawing the racks and exposure to the open 

 air. Shirts and collars instantly assume the crisp dryness they 

 possessed before exposure, losing the musty smell of long packing 

 in a trunk. Silks, laces, and the most delicate woollen goods show 

 no signs of injury whatever from the treatment. Articles of leather, 

 rubber, and whalebone would be injured by the heat, and are 

 therefore disinfected with the bichloride-of-mercury solution. The 

 time required to charge the chamber with apparel for disinfection 

 is thirty minutes ; time required for action of moist heat, twenty 

 minutes ; for removal of articles, fifteen minutes, — a total of sixty- 

 five minutes. 



The report of Dr. Holt is amply illustrated with figures of the 

 apparatus used in disinfection, and the method of its application, 

 and should be in the possession of every sanitarian as furnishing 

 a model which can be adapted to the requirements of every quaran- 

 tine station. 



MENTAL SCIENCE. 

 Ideas of Number in Animals. 



The study of comparative psychology labors under two difficul- 

 ties : the facts upon which it is to build cannot be accurately ascer- 

 tained without great difficulty ; and the intrepretation of the facts 

 is a still more delicate and laborious task. Civilized man has looked 

 upon the facts of nature with so entirely a modern mind, that it is 

 a rare gift to be able to appreciate the elementary thought-pro- 

 cesses of uncivilized communities or of animals. Every attempt at 

 improving the methods of presenting these phenomena should be 

 received with sympathetic consideration, without regarding as final 

 what is probably only a step to something better. Mme. Clemence 

 Royer has recently made a study of the mathematical powers of 

 animals that deserves the consideration of all students of psychol- 

 ogy- 



Among men we find all grades of mathematical ability, from that 

 of a Newton and Laplace to that of one who cannot conceive the 

 abstract notion of number. What the savage lacks is not the 

 knowledge of the difference between three men and ten men, but 

 the power to abstract the notion ' three ' from men, trees, hands, 

 and so on. The first step in this process is the distinction of unity 

 from plurality, then of duality, etc., from plurality. The relic of this 

 appears in the prevalence of the dual number in rudimentary 

 languages. 



What impresses itself upon the primitive mind is the sensory 

 images of objects : he knows the difference between four trees ar- 

 ranged in a quadrilateral and in a row, between the general look of 

 three trees and of four trees, but cannot see any thing in common 

 between four trees and four stones. He is a poor arithmetician, 

 but a good geometer ; he is impressed by space relations, not by 

 numerical characteristics. He can judge of distance, of the outlines, 

 of the sizes of objects, but all by an instinctive visual talent. If, 

 then, arithmetical notions appear late in human development, we 

 can hardly expect it to be prominent among animals, lacking an 

 intellectual language. What we can speak of as the language of 

 animals is limited to the expression of the emotions. Their 

 mathematical distinctions are sensory in nature. They distinguish 

 between unity and plurality of certain objects, but we cannot credit 



them with abstract notions of 'one' and 'two.' They have a 

 kaleidoscopic, photographic memory, not an abstract verbal one. 

 All the wonderful powers of animals finding their way, of regularity 

 in time, must be accounted for by an accuracy in the perception of 

 outlines, and the unconscious registration of general intervals by 

 feelings of fatigue, number of steps, and so on. 



There is no unit of distance or time. Distance is to them a 

 perception, not an idea. Just so a dog, in attacking a boar, accu- 

 rately judges the length of his leap, the size and strength of the 

 enemy; but this does not involve any mathematical calculations. 

 The apparent understanding of language by trained dogs comes 

 under the same head. The dog does not appreciate the phonetic 

 value of the words, but takes his clew from the intonation, the little 

 gestures, and the like. The horse understands the 'language of the 

 bit ' better than that of his master. Animals, in brief, have their 

 geometrical sense of relations well developed (better than men in 

 some respects), but are not arithmeticians. 



They do not, however, lack all appreciation of number. They do 

 distinguish between numbers, for this is necessary to their exist- 

 ence ; but their distinction, when it goes above a few simple units, 

 is in the form of a bunch-estimate, depending as much on the ar- 

 rangement of the group as on its size. They cannot estimate as 

 we do when we divide an army into regiments, into companies, and 

 so on, and thus estimate the number of men. 



Birds, it is true, are much alarmed if an egg be removed from 

 their nests, but they are equally alarmed if the arrangement of the 

 eggs be disturbed ; thus indicating that it is the general disturbance 

 that causes the alarm, not a counting of the eggs. The mother 

 recognizes her young individually, and thus can notice the absence 

 of one ; but she probably sees no more difference between the eggs 

 than we do, and judges their number only by their arrangement. 

 Cats probably distinguish their young by differences in the fur, and 

 so on : they are little affected if one kitten be removed ; but, if more 

 than four be taken away, they are greatly disturbed, and especially 

 so if but one be left. If the kittens are weaned, the loss is not taken 

 so seriously. 



Dogs notice the absence of one of their number ; but that they 

 recognize each other individually is shown by their preferences 

 and jealousies, both among themselves and towards men. Shep- 

 herds' dogs do not count their fold, but simply have a general pic- 

 ture of its size. Likewise trained dogs do not count, but have 

 simply learned to associate mechanically certain geometrical forms 

 with certain actions. Sir John Lubbock's dog, that brings a different 

 label according as it wants something to eat, to go out, and so on, 

 does not appreciate the intellectual value of the letters, but regards 

 the label as an artificial means for gaining certain ends. The dog's 

 faculties in these respects, however, seem to be not inferior to those 

 of the Bushmen, who count only to two, and call all above that 

 ' many.' Number is here concrete only with reference to objects 

 where plurality is a useful trait : it is never abstract, and so can no 

 more reach the stage of mathematical art than can their emotional 

 language reach the stage of ideational abstraction to which ours 

 has attained. By this is not meant that animals can form no ab- 

 stract notions, but that their general notions are very limited in 

 scope, and are along the line of directly useful interests only. The 

 animal thinks by generic images, does not err in its judgments, is 

 not liable to fallacies, all of which are distinctly human because we 

 think by the intervention of words ; and this difference forms the 

 difficulty of our communication with them. 



Animal-trainers have ignored these facts, not recognizing that 

 geometry is more fundamental than arithmetic, and have attempted 

 to make animals arithmeticians when nature has made them geom- 

 eters. Ourselves accustomed to look on every thing from its 

 numerical aspect, we fail to see how trivial a part this plays in 

 animal life. 



There remains the consideration of number, not of objects in 

 space, but of succession in time. This faculty has been claimed 

 for the higher animals. There are many stories of pets keeping up 

 the same action at regular intervals, and always the same number 

 of times per day or per week, — the story of a dog who always 

 wanted three pieces of sugar, of the dog who would always keep 

 out of the way on Sunday, and so on. Mme. Royer explains this 

 as due to ordinary associations without the intervention of abstract 



