666 



RESPIRATION 



sometimes by hollow ' skin gills ' M well. The 

 crustaceans usually breathe Ity gills or through 

 the Hkin ; in I'eripatus, Myrin|KMls, HIII! inserts 

 nir-till>e or trachea- ramify throughout the body. 

 Scor|iions have plaited sacs or 'lung- book*,' which 

 niiinv regard <u> modifications of traclien- ; and these 

 are developed in spiders also, with or, rarely, with- 

 out tin- addition of orilinary air-tuhea. The king- 

 crab has a unique arrangement, consisting of 

 plaited sacs or ' gill-liookii,' adapted for breathing 

 in water. Some molluscs breathe simply by the 

 skin, others have external gills, monk have gills 

 sheltered l>v the mantle, anil air-breathing forms 

 like snails have a mantle-cavity which serves as a 

 lung. In Kalanoglosstis there are numerous res- 

 piratory clefts opening from the pharynx to the 

 exterior; Appendiculana and young Tiinicates have 

 a pair of these ; in adult Tunicate- the primitive 

 clefts are replaced by numerous secondary slits on 

 the wall of the pharynx, through which water 

 drawn in by the mouth passes into an atrial or 

 peribranchidl chamber and thence to the exterior ; 

 the same is true of Amphioxus. Clefts from the 

 wall of the pharynx to the exterior are, indeed, 

 characteristic of vertebrates, but beyond amphibians 

 they are transitory embryonic structures, never 

 used for breathing. This loss of functional gill- 

 clefts is associated partly with the development of 

 an embryonic birth-robe known as the allantois, 

 which secures the aeration of the embryo's blood, 

 and partly with the transition from aquatic to 

 terrestrial life. In the hagfish the nasal sac opens 

 into the mouth ; in fishes this is only true of the 

 double-breathing Dipnoi ; in all other vertebrates 

 air passes through the nostrils in and out of the 

 mouth and lungs. In the hag and lamprey there 

 are purse-like gill -pockets, and the respiratory 

 arrangements are otherwise peculiar. In fishes 

 gill-filaments are borne on the skeletal arches 

 separating the gill-clefts, and the blood-vessels 

 spread out on the filaments are washed by currents 

 of water. Young Elasmobranchs have at first ex- 

 ternal gills and afterwards the internal gills charac- 

 teristic of all fishes. The Dipnoi have gills, but 

 they also come to the surface and gulp air, using 

 their air-bladder as a lung, and thus pointing the 

 way to amphibians. For, while almost all am- 

 phibians have gills in their youth, all the adults 

 are lung-breathers, though some retain their gills 

 as well. Among higher vertebrates there are 

 many peculiarities, such as the single lung of 

 most serpents, the balloon-like air-sacs around the 

 lungs of birds, and the adaptations of cetaceans 

 as aquatic lung-breathers, but the essential charac- 

 teristics of pulmonary respiration are the same in 

 all. The hienioglobin, so important 

 in respiration, occurs first in Nemer- 

 teans, and is present in some other 

 worms, some Echinoderms, a few 

 Arthropod-, some molluscs, and in 

 all vertebrates except the Tunicate*. 

 . \mpliioxus, and a few exceptional 

 tishcs. Hut though hicmogloliin is 

 not present in most invertebrates, 

 Analogous pigments are common, 

 especially one called hnmoryanin t 

 M-hicli turns bluish when oxidised. 



AHTIKICIAI, KKSIMRATION. When 

 death is imminent owing to a cessa- 

 tion of the natural respiration movements, it may 

 Kometimes be averteu by an imitation of them 

 carried on regularly for some time. Such a 

 condition may occur in disease (e.g. asthma, 

 epilepsy), though very rarely; it is most common 

 in suffocation, either by drowning, choking, or 

 strangulation, and in sometimes met with also 

 in iHiisoning by noxious vapours (e.g. carbonic 

 acid, carbonic oxide, coal-gas, chloroform, &c.). 



In order that any method may have a chance of 

 U'ing successful it U of course necessary that the 

 entrance uf air into the lungs be not impeded, 

 either by a piece of food or by water in the wind- 

 pipe, or by the tongue falling back and closing the 

 upper opening. A piece of food may sometimes he 

 removed through the mouth by the finger ; if this 

 fails the windpipe should be opened (see TRAOIK- 

 OTOMY). In those apparently drowned the body 

 should first be laid on the face, with the head low, 

 and the thorax and abdomen pressed upon in order 

 to expel fluids which may have been drawn into 

 the trachea and bronchial t ulies. The tongue may 

 need to be held forward ; this may be done by an 

 assistant, or an elastic band passed round the 

 tongue and the chin will effect the object. 



Numerous different methods have been devised 

 for effecting the objects aimed at, and no general 



Fig. 1. 



consensus of opinion has yet been arrived at as to 

 which is the best. The methods fall into three 

 divisions : ( 1 ) insufflation, or blowing of air into 

 the lungs, either by the mouth or by means of 

 bellows ; (2) manual methods, in which external 

 manipulations of the chest-walls are made to elleet 

 the entrance and exit of air; (3) electrical stimu- 

 lation of the respiratory muscles. In all cases 

 where artificial respiration is required every 

 moment is of importance. It is doubtful whether 

 life can ever be restored when the heart has ceased 

 to beat for more than a few seconds ; and when 

 breathing has stopped failure of the heart's action 

 is always imminent. That method is therefore 

 best which can be applied with the least possible 

 loss of time, so that under ordinary circumstances 

 the methods which require bellows or electric 

 batteries are out of the question. Direct insuffla- 

 tion, or blowing of air into the patient's lungs by 

 the mouth applied to his mouth, is now hardly 

 ever used except in the case of very young chil- 

 dren. Of the manual methods those most in use 



Fig. 2. 



are Marshall Hall's (1856), Silvester's (1857), and 

 Howard's (1877). The second is certainly the 

 most easy to learn, hut is more fatiguing to carry 

 out for a length of time than either of the others. 

 In Marshall Hall's method the body is laid upon 

 its face and rolled 'in what may be 'termed cradle 

 fashion ' from this position on to one side and a 

 little Key on,! it (inspiration), and then back on to 

 the face (expiration). In Silvester's method the 



