NERVE REFLEXES IN ANIMALS 263 



forcibly distend or open the two ventricles. The theory further declares that the two ventricles, when they close 

 or contract, forcibly distend or open the two auricles. The forcible distension is said to be due to the blood acting 

 as a fluid wedge. The closing contracting movements are considered vital, the opening distending ones passive. 

 As a matter of fact, both sets of movements are vital. They are, moreover, spontaneous and independent of each 

 other. They are not mechanical movements brought about by the blood and certain reflex acts, in conjunction 

 with irritability and stimulation. Against the mechanical theory it will suffice if I state that the heart contracts 

 and dilates spontaneously by centripetal and centrifugal movements when cut out of the body, deprived of its 

 blood, and placed in an exhausted receiver. I may be permitted to add that the muscular walls of the auricles 

 are so thin and feeble as to be altogether incapable of forcibly opening the ventricles, the walls of which are so thick 

 that they, in many cases, form a solid muscular mass at the beginning of the systole. The remarks now made 

 may with equal cogency be applied to the lymphatic hearts of the frog. 



7. The movements of respiration. — These are said to be due to reflex acts caused (a) by the presence of carbonic 

 acid in the air-cells and air-passages ; (b) to the accumulation of carbonic acid in the veins ; and (c) to cold acting 

 on the skin, &c. The difficulties already referred to reappear in a slightly altered form. The respiratory move- 

 ments are, as is well known, co-ordinated, rhythmic, alternating movements — that is, movements occurring in opposite 

 directions at stated intervals. Now it need scarcely be explained that the presence of carbonic acid in the lungs 

 and veins, and the application of cold to the sldn, could not by any possibility account for the give-and-take, opening 

 and closing movements of the chest. The air and carbonic acid in the lungs at any given time vary Uttle, and the 

 latter may, for all practical purposes, be regarded as constant. It could not, by any process known to chemistry, 

 act as an irritant and produce the opening of the chest the one instant, and immediately after act as a non-irritant 

 and produce the closing of the chest. But nothing short of this could, if the mechanical views which prevail are 

 true, produce the alternate opening and closing of the chest as witnessed in respiration. 



8. The first respiration of the child. — The first respiration is said to be due to cold acting on the skin and other 

 parts. Here again, cold (a single cause) is assumed to produce double and opposite results. If cold produced 

 inspiration it could not within a second or two produce expiration. The cold is not alternately laid on and cut off, 

 which it would require to be if it were tbe real cause of the double movements referred to. The cold is present both 

 dming the inspiratory and expiratory movements. This fact is, of course, wholly at variance with the theory of 

 irritability and stimulation in their relation to reflex acts. 



9. The sense organs. — These are also said to be largely under the influence of reflex nerve centres, but the 

 subject of reflexes need not be further considered here, as I refer to them further on when discussing the nature of 

 respiration. 



A consideration of rhythms in plants and animals necessarily involves a consideration of the so-called reflexes 

 in their entirety. Strictly speaking, reflex movements are confined to animals with a nervous system, consisting 

 of a brain, spinal cord, and sensory and motor nerves — the brain, for convenience and the purposes of experiment, 

 being practically eliminated. Their peculiarity consists in their involuntary nature — that is, they occur in animals 

 through the instrumentality of the spinal cord and sensory and motor nerves as apart from, and largely to the 

 exclusion of, the brain. The illustration usually given is the living decapitated frog. It is found that if the frog so 

 mutilated has a hind foot pricked, lacerated, or stimulated in some way, it fiexes and draws up the leg of which 

 the foot forms a part : it removes it from the source of irritation. If, further, a little mustard be applied to the 

 inside of one of the thighs of the frog, it scrapes away the offending mustard with the foot of the opposite leg. Here 

 there is a low form of cognition and intelligence which can manifest itself apart from, and independently of, the 

 brain. Similar results can be obtained in the human subject suffering from paralysis of the lower extremities (para- 

 plegia), when, because of disease of the brain or upper part of the spinal cord, the brain, as an integral part of the 

 nervous system, is practically removed. In such cases, the ganglia or nerve centres of the spinal cord and the 

 sensory and motor nerves (their connection with the brain excepted) are intact, and in perfect working order. My 

 explanation of the phenomenon is that the nervous system in certain cases can work voluntarily and refiexly apart 

 from the brain, and that animals with ganglia, and sensory and motor nerves (minus a brain and cord) — say the five- 

 rayed star-fish — can also act voluntarily. This the mechanical school of physiology deny. They insist that the 

 movements of the star-fish are automatic, reflex movements. The mechanical theory of the movements of the star- 

 fish is disproved by observation and experiment. The star-fish certainly can and does move voluntarily, as any one 

 may satisfy himself who studies it in its native habitat. Indeed, voluntary movements, of a kind, take place in 

 both plants and animals where neither a nervous system nor a brain can be detected. 



While it would be a mistake to deny a low form of cognition and intelUgence to the decapitated frog, it would 

 be even a greater mistake to deny the power of voluntary movement to the star-fish. In other words, experiments 

 on the frog such as those referred to do not afford warrant for classing the movements of the star-fish, and of animals 



