At the present moment it is impossible to draw up any definition, based on broad anatomical or developmental characters, by which any one of Cuvier's great groups shall be separated from all the rest.
The discovery of a single fossil creature in a geological stratum of a wrong period, the detection of a single anatomical or physiological fact irreconcilable with origin by descent with modification, would have been destructive of the theory and would have made the reputation of the observer.
When a series of the modifications of an anatomical structure has been sufficiently examined, it is frequently possible to decide that one particular condition is primitive, ancestral or central, and that the other conditions have been derived from it.
It is necessary to determine if the modification be a simple change that might have occurred in independent cases, in fact if it be a multiradial apocentricity, or if it involved intricate and precisely combined anatomical changes that we could not expect to occur twice independently; that is to say, if it be a uniradial apocentricity.
In 18J5, however, Owen included under Lamarck's term Radiaria the Echinodermata, Anthozoa, Acalepha and Hydrozoa, while Agassiz also clung to the term Radiata as including Echinodermata, Acalepha and Polypi, regarding their separation into Coelenterata and Echinodermata as "an exaggeration of their anatomical differences" (Essay on Classification, London, 1859).
However, Nitzsch had not as yet seen his way to proposing any methodical arrangement of the various groups of birds, and it was not until some eighteen months later that a scheme of classification in the main anatomical was attempted.
The anatomical construction of these plants presents many peculiarities which have given rise to discussion as to the allocation of the order among the dicotyledons or among the monocotyledons, the general balance of opinion being in favour of the former view.
A great deal of work still remains to be done in this department, which at the present time affords one of the most promising fields of anatomical investigation.
A very considerable body of knowledge relating to this subject already exists, but further work on experimental lines is urgently required to enable us to understand the actual economy of plants growing under different conditions of life and the true relation of the hereditary anatomical characters which form the subject matter of systematic anatomy to those which vary according to the conditions in which the individual plant is placed.
This view requires the existence of certain anatomical arrangements to secure the isolation of the separate columns, and cannot be said to be fully established.
The scope of the anatomical part of the following article is a general account of the structure of birds (A y es) in so far as they, as a class, differ from other vertebrates, notably reptiles and mammals, whilst features especially characteristic, peculiar or unique, have been dwelt upon at greater length so far as space permitted.
That chapter of comparative anatomy (together with other anatomical details, for which see the separate articles) is now dealt with in the article Skull; here only the most avine features are alluded to, and since some of Parker's original illustrations have been retained, the description has been shortened considerably.
It is, however, fair to state that his system was not built entirely upon these muscular variations, but rather upon a more laborious combination of anatomical characters, which were so selected that they presumably could not stand in direct correlation with each other, notably the oil-gland, caeca, carotids, nasal bones and above all, the muscles of the thigh.
That Garrod has so very much advanced the classification of birds is ultimately due to his comprehensive anatomical knowledge and general insight.
Attempts to derive the anacromyodian and the katacromyodian from the diacromyodian condition are easy on paper, but quite hopeless when hampered by the knowledge of anatomical facts and how to use them.
Classical anatomical memoirs are those of L.
One of the possibilities to be allowed for is that of exceptional muscular endowment or anatomical peculiarity in the medium.
It is noteworthy that in this family only among the Polychaeta, the nephridia are not restricted to a single pair in each segment; so that the older view that the gonad ducts are metamorphosed nephridia is not at variance with the anatomical facts which have been just stated.
This is the largest group of Mollusca, including nearly sixty families, some of which are insufficiently known from the anatomical point of view.
Yet it was regarded " as being the one which facilitates the expression of the leading anatomical differences which obtain in the class of birds, and which therefore may be considered as the most natural."
Macgillivray himself it was, apparently, who first detected the essential difference of the organs of voice presented by some of the New-World Passerines (subsequently known as Clarnatores), and the earliest intimation of this seems to be given in his anatomical description of the Arkansas Flycatcher, Tyrannus verticalis, which was published in 1838 (Ornithol.
Herein the author first assigned anatomical reasons for rearranging the order Anseres of Linnaeus and Natatores of Illiger, who, so long before as 1811, had proposed a new distribution of it into six families, the definitions of which, as was his wont, he had drawn from external characters only.
As has been stated, the first of this series of anatomical descriptions appeared in the fourth volume of his work, published in 1838, but they were continued until its completion with the fifth volume in the following year, and the whole was incorporated into what may be termed its second edition, The Birds of America, which appeared between 1840 and 1844.
Carrying on the work from the anatomical point at which he had left it, correcting his errors, and utilizing to the fullest extent the observations of Keyserling and Blasius, to which reference has already been made, Muller, though hampered by mistaken notions of which he seems to have been unable to rid himself, propounded a scheme for the classification of this group, the general truth of which has been admitted by all his successors, based, as the title of his treatise expressed, on the hitherto unknown different types of the vocal organs in the Passerines.
In the anatomical field the work of Malpighi and Swammerdam was at first continued most energetically by French students.
Many anatomical and developmental details were carefully worked out by L.
The medical school, a department of Washington University, includes laboratory, anatomical, clinical and other buildings.
Of the precise anatomical, not to say the physiological, knowledge which appears to be displayed by the insect in stinging only the nerve-centres of its prey.
Albuminoids is the anatomical name given to albuminous substances forming the connective tissues.
The position of the Arachnida in the great sub-phylum Arthropoda, according to recent anatomical and embryological researches, is explained in the article Arthropoda.
Miller's Squamata and Nuda (1832), are merely new names for de Blainville's Ornithoides and Ichthyoides, though Muller gave far better anatomical characters of the two groups than had previously been put forward.
Indeed, the historical and present importance of this aspect or branch of zoological science is so great that the name " zoology " has until recently been associated entirely with it, to the exclusion of the study of minute anatomical structure and function which have been distinguished as anatomy and physiology.
Anatomy and the study of animal mechanism, animal physics and animal chemistry, all of which form part of a true zoology, were excluded from the usual definition of the word by the mere accident that the zoologist had his museum but not his garden of living specimens as the botanist had; 1 and, whilst the zoologist was thus deprived of the means of anatomical and physiological study - only later supplied by the method of preserving animal bodies in alcohol - the demands of medicine for a knowledge of the structure of the human animal brought into existence a separate and special study of human anatomy and physiology.
Owing to the connexion of medicine with these seats of learning, it was natural that the study of the structure and functions of the human body and of the animals nearest to man should take root there; the spirit of inquiry which now for the first time became general showed itself in the anatomical schools of the Italian universities of the 16th century, and spread fifty years later to Oxford.
Gradually since the time of Hunter and Cuvier anatomical study has associated itself with the more superficial morphography until to-day no one considers a study of animal form of any value which does not include internal structure, histology and embryology in its scope.
Extended until it formed a sufficient body of knowledge to serve as an anatomical basis for classification.
The commencement of anatomical investigations deserves notice here as influencing the general accuracy and minuteness with which zoological work was prosecuted, but it was not until a late date that their full influence was brought to bear upon systematic zoology by Georges Cuvier (1769-1832).
Z considerable use of anatomical characters in his definitions of larger groups, and may thus be considered as the father of modern zoology.
1 The anatomical error in reference to the auricles of Reptiles and Batrachians on the part of Linnaeus is extremely interesting, since it shows to what an extent the most patent facts may escape the observation of even the greatest observers, and what an amount of repeated dissection and unprejudiced attention has been necessary before the structure of the commonest animals has become known.
See, for anatomical details, Alimentary Canal.
The museum contains a valuable collection of anatomical and surgical preparations.
Of this contribution to science, as of all the rest which have since proceeded from him, may be said in the words he himself has applied (ut supra, p. 271) to the work of another labourer in a not distant field: " This is a model paper for unbiassed observation, and freedom from that pleasant mode of supposing instead of ascertaining what is the true nature of an anatomical element."