October 13, 1893.] 



SCIENCE. 



205 



pology in the University of Naples; Dr. Eiccardi, decent 

 of anthropology in the University of Modena; and many 

 others whose vforks have secured them vpell-earned titles 

 of honor. 



Professor Sergi himself is one of the most industrious 

 of anthrojiologists. Within the present year I have seen 

 from his pen a learned essay on the "Principles and 

 Methods of Classifying the Human Race,'' by craniological 

 forms; a "Sj'stematic Catalogue of the Varieties of Man 

 found in Russia;" and a Report on the Anthropological 

 Congress in Moscow in 1892. No doubt under his active 

 guidance the new society will have a prosperous career. 



NOTES OF SOME EXPERIMENTS ON THE HOUSE- 

 FLY.* 



Bl' JOHN B. SMITH, SC. D., BDTGERS COLLEGE, NEW BRUNSWICK, N. J. 



Insects, in some circumstances, exhibit a tenacity of 

 life which is extremely surprising. They will stand a 

 great deal of mutilation, apparently without manifesting 

 pain, and will get along quite comfortably on a minimum 

 allowance of wings and legs 



The house-flj' is about as common an insect as we have, 

 and I was led recently to try some experiments with a 

 view to locate, as nearly as might be, the seat of life — or 

 rather the controlling nerve centre, for life exists in each 

 cell — in this insect. A number of flies were captured and 

 decapitated. This process, of course, severed not only 

 the nervous cord, and separated the brain from the rest 

 of the body, but it cut as well the alimentary canal, and 

 the main blood vessel, the Aorta. Flies so treated lived 

 from ten to sixteen hours. They had, of course, lost all 

 sense of direction; but had not lost the use of any of 

 their limbs. When they were touched with the point of 

 a needle they would walk away; but always in a straight 

 line, and without attempting to avoid any obstacle that 

 might have been in the way; if the annoyance was more 

 than a little, they would attempt to fly. As in the former 

 case, they were unable to direct themselves, and as soon 

 as they met with an obstacle would rest quietly until 

 again irritated. So long as they were left undisturbed 

 they remained at rest, or if a pencil was presented to them 

 between the fore legs, they would crawl up for a short 

 distance, and again rest quietly. In such cases it was 

 rather difficult to make them loosen their hold; they 

 would cling tightly, and would not, if they could avoid it, 

 loosen their grasp until something else was i^resented to 

 them to which they could attach themselves. There 

 seemed to be a realization that something was wrong, 

 and occasionally the front legs would pass over the place 

 where the head ought to be; but there was not at any 

 time what could be considered as a manifestation of pain. 



From another set of flies the abdomen was cut. This 

 severed the nervous cord, the heart and the digestive 

 system including in the latter almost all save the ossopha- 

 gus. These insects lived for from six to ten hours, and 

 for a large jjortion of the time they were active, flying 

 about and running, and in fact behaving themselves like 

 insects that were in all respects normal. As in the other 

 case there seemed to be no active manifestation of pain. 

 For a short time, say half a hour after the abdomen was 

 severed, the insects were constantly extending and with- 

 di'awing the proboscis, evidently realizing that some- 

 thing was wrong, in that connection. At no time was 

 there any interference with the power of motion, either 

 of the legs or wings, and in fact it was impossible to see 

 any difference between their case and those of perfectly 

 normal flies, under the same circumstances and confined 

 with them. 



*Read before Section F., at the Madison meetina; of the A. A. 

 A. S. 



Perhaps a few words of explanation concerning the 

 gross anatomy of the fly may not be entirely out of place 

 in order that my experiments may be better understood. 

 Insects, generally, have only a single blood vessel, ex- 

 tending the full length of the body, and lying just be- 

 neath the dorsum, or upper surface. The digestive sys- 

 tem occu23ies a large portion of the abdomen, and the 

 central part of the thorax. The nervous system extends 

 the full length of the body, in the form of a double cord, 

 on which there are at somewhat irregular intervals en- 

 largements or ganglia, and it lies on the floor of the 

 body, just above the under surface. That ganglion 

 which is situated in the head, is called the brain. We 

 have seen that severing the brain from the rest of the 

 body did not kill the insect; the severed head in no case 

 showed any power of motion in any of its parts, no mSit- 

 ter what means were taken to excite it. So long as the 

 head was left attached to the body, even if the abdomen 

 had been cut off, all the mouth parts, and the antennae 

 could be readily excited and made to move. No insect 

 that had been mutilated by cutting off the abdomen 

 could be induced to feed or attempt feeding. Cutting off 

 all that i^art of the nervous cord that was situated in the 

 abdomen produced no interference with the powers of 

 motion. From another set of specimens both head and 

 abdomen were removed, leaving only the thorax with its 

 appendages; how much life remained in the abdomen it 

 was impossible to say, since it contained no appendages 

 that could be readily stimulated. The head, as already 

 mentioned, soon died; but the thorax alone retained life 

 for more than six hours, and these fragments of insects 

 could be readily made to walk, although rarely could 

 they be induced to make use of the wings. Yet if one 

 were held up by the legs with forceps, the wings would 

 be used in trying to escape, and would buzz as lively as 

 if the insect was in full possession of all faculties. 



Prom a number of other specimens the abdomen and 

 that portion of the thorax containing the hind legs were 

 removed. These specimens lived for from five to six 

 hours. Both fore and middle legs remained perfectly 

 active, and the mouth jjarts were readily stimulated. The 

 hind legs could not be stimulated even where that portion 

 of the thorax bearing them remained attached to the abdo- 

 men. 



Another set of specimens was treated as were those last 

 mentioned, except that the head also was removed. Here 

 two-thirds of the thorax, containing two pairs of legs, re- 

 mained alive quite as long as when the head was attached 

 to it ; the i^resence or absence of the brain appearing to 

 make no difference. Other specimens were taken and 

 these were cut in two between the first and second pairs 

 of legs. The anterior p rt, containing the head and fore 

 legs, remained alive for from four to five houi's, although 

 of course incapable of moving about. It was easy to in- 

 duce an insect so treated to extend its tongue, and indeed 

 this was done quite frec^uently by the insect even without 

 stimulation. The legs were passed at intervals over the 

 front of the head and there was no difficulty in exciting 

 them to motion by merely touching with a needle or any 

 similar instrument. That jjart of the insect containing the 

 middle and hind legs and the abdomen seemed devoid of 

 active life, and it was impossible to induce these struc- 

 tures, or the wings, to move, within a very few moments 

 after the operation. Another set of specimens was treated 

 exactly as those last mentioned save that here the head 

 also was cut off. In this case the fragment of the thorax 

 containing the front legs lived for three houi-s, while the 

 other portions of the insect were apparently dead a very 

 few minutes after the operation. An insect cut in half 

 through the prothorax died almost immediately, neither 

 portion responding to such stimuli as I employed, more 

 than a very few moments after. 



