512 



SCIENCE. 



asleep ; the muscles are at one moment in severe exercise, 

 the next in complete repose; the liver, which before a 

 meal is inactive, during the process of digestion is turgid 

 with blood, and busily engaged in the chemical work 

 which belongs to it. For all these vicissitudes the tract 

 of grey substances which we call the vascular centre has 

 to provide. Like a skilful steward of the animal house- 

 hold, it has, so to speak, to exercise perfect and unfailing 

 foresight, in order that the nutritive material which 

 serves as the oil of life for the maintenance of each vital 

 process, may not be wanting. The fact that this won- 

 derful function is localized in a particular bit of grey sub- 

 stance is what is meant by the expression " automatic 

 action of a centre." 



But up to this point we have looked at the subject from 

 one side only. 



No state ever existed of which the administration was 

 exclusively executive — no government which was, if I 

 may be excused the expression, absolutely absolute. If 

 in the animal organism we impose on a centre the re- 

 sponsibility of governing a particular mechanism or pro- 

 cess, independently of direction from above, we must give 

 that centre the means of being influenced by what is go- 

 ing on in all parts of its area of government. In other 

 words, it is essential that there should be channels of in- 

 formation passing inwards, as there should be channels 

 of influence passing outwards. Now what is the nature 

 of these channels of information ? Experiment has taught 

 us not merely with reference to the regulation of the cir- 

 culation, but with reference to all other automatic 

 mechanisms, that they are as various in their adaptation 

 as the outgoing channels of influence. Thus the vascular 

 centre in the medulla oblongata is so cognizant of the chem- 

 ical condition of the blood which flows through it, that if too 

 much caroonic acid gas is contained in it, the centre acts 

 on information of the fact, so as to increase the velocity 

 of the blood-stream, and so promote the arteriahzation of 

 the blood. Still more strikingly is this adaptation seen in 

 the arrangement by which the balance of pressure and 

 resistance in the blcod-vessels is regulated. The heart, 

 that wonderful muscular machine by which the circula- 

 tion is maintained, is connected with the centre, as if by 

 two telegraph wires — one of which is a channel of influ- 

 ence, the other of information. By the latter the engineer 

 who has charge of that machine sends information to 

 headquarters whenever the strain on his machine is ex- 

 cessive, the certain response to which is relaxation of the 

 arteries and diminution of pressure. By the former he is 

 enabled to adapt its rate of working to the work it has to 

 do. 



If Dr. Whytt, instead of cutting off the head of his frog, 

 had removed its brain — i. e., the organ of thought and 

 consciousness — he would have been more astonished than 

 he actually was at the result ; for a frog so conditioned 

 exhibits, as regards its bodily movements, as perfect 

 adaptiveness as a normal frog. But very little careful 

 observation is sufficient to show the difference. Being 

 incapable of the simplest mental acts, this true animal 

 automaton has no notion of requiring food or of seeking 

 it, has no motive for moving from the place it happens to 

 occupy, emits no utterance of pleasure or distress. Its 

 life processes continue so long as materia] remains, and 

 are regulated mechanically. 



To understand this all that is necessary is to extend 

 the considerations which have been suggested to us in 

 our very cursory study of the nervous mechanism by 

 which the working of the heart and of arteries is gov- 

 erned, to those of locomotion and voice. Both of these 

 we know, on experimental evidence similar to that which 

 enables us to localize the vascular centre, to be regulated 

 by a centre of the same kind. If the behavior of the 

 brainless frog is so natural that even the careful and in- 

 telligent observer finds it difficult to attribute it to any- 

 thing less than intelligence, let us ask ourselves whether 

 the chief reason of the difficulty does not lie in this, that 



the motions in question are habitually performed intelli- 

 gently and consciously. Regarded as mere mechanisms, 

 those of locomotion are no doubt more complicated than 

 those of respiration or circulation, but the difference is 

 one of degree, not of kind. And if the respiratory move- 

 ments are so contrclled and regulated by the automatic 

 centre which governs them, that they adapt themselves 

 perfectly to the varying requiiements of the organism, 

 there is no reasoa why we should hesitate in attributing 

 to the centres which preside over locomotion powers 

 which are somewhat more extended. 



But perhaps the question has already presented itself 

 to your minds. What does all this come to ? Admitting 

 that we are able to prove (i) that in the animal body. 

 Product is always proportional to Process, and (2) as I 

 have endeavoured to show you in the second part of my 

 discourse, that Descartes' dream of animal automatism 

 has been realized, what have we learnt thereby? Is it 

 true that the work of the last generation is worth more 

 than that of preceding ones? 



JURASSIC BIRDS AND THEIR ALLIES* 



Bv Professor O. C. Marsh. 



About twenty years ago, two fossil animals of great 

 interest were found in the lithographic slates of Bavaria. 

 One was the skeleton of Arclnvopteryx, now in the 

 British Museum, and the other was the Compsognatkus 

 preserved in the Royal Museum at Munich. A single 

 feather, to which the name Arckwopteryx was first ap- 

 plied by Von Meyer, had previously been discovered at 

 the same locality. More recently, another skeleton has 

 been brought to light in the same beds, and is now in 

 the Museum of Berlin. These three specimens of 

 Arckcropteryx are the only rema'ns of this genus known, 

 while of Compsognatkus the original skeleton is, up to 

 the present time, the only representative. 



When these two animals were first discovered, they 

 were both considered to be reptiles by Wagner, who de- 

 scribed Compsoifnat/ius, and this view has been held by 

 various authors down to the present time. The best au- 

 thoiities. however, now agree with Owen that Archceop- 

 tervx is a bird, and that Compsognatkus, as Gegenbaur 

 and Huxley have shown, is a Dinosaurian reptile. 



Having been engaged for several years in the investi- 

 gation of American Mesozoic birds, it became important 

 for me to study the European forms, and I have recently 

 examined with some care the three known specimens of 

 Arckwopteryx. I have also studied in the Continental 

 Museums various fossil reptiles, including Compsogna- 

 tkus, which promised to throw light on the early forms 

 of birds. 



During my investigation of Archceopteryx, I observed 

 several characters of importance not previously deter- 

 mined, and I have thought it might be appropriate to 

 present them here. The more important of these char- 

 acters are as follows : — 



1. The presence of true teeth, in position, in the skull. 



2. Vertebra; biconcave. 



3. A well-ossified, broad sternum. 



4. Three digits only in the manus, all with claws. 



5. Pelvic bones separate. 



6. The distal end of fibula in front of tibia. 



7. Metatarsals separate, or imperfectly united. 

 These characters, taken in connexion with the free 



metacarpals, and long tail, previously described, show 

 clearly that we have in Arckcropteryx a most remark- 

 able form, which, if a bird, as I believe, is certainly the 

 most reptilian of birds. 



If now we examine these various characters in detail, 

 their importance will be apparent. 



The teeth actually in position in the skull appear to be 



♦Read before Section D., British Association for the Advancement of 

 Science, at York, Sept. 2, 1881. 



