We may now briefly consider the genetic, histological and mechanical conditions which the above-outlined course of development imposes on the alimentary tract.
Subsequently differentiation of this simple tube into successive segments takes place, marked by differences in shape and caliber and in histological structure.
It does not fall within the province of this work to treat from a histological standpoint the changes which take place in the uterine walls during pregnancy.
The early histological changes in the cells of the notochord are approximately the same in all the Craniata.
At the side of the optic ganglion is a peculiar body, known as the white body (not shewn in the figure), which has the histological characters of glandular tissue.
These papillae are very probably sensitive structures; but I have not yet investigated their histological characters.
The causes which give rise to a retardation of histological differentiation will be dealt with in the second part of this chapter which deals with larval characters and larval forms.
The histologicalelements become more differentiated, and a few organs reach a fuller development.
For the histologicaldetails as to the formation of these various organs I must refer the reader to treatises on histology, confining my attention here to the general embryological processes which take place in their development.
This primitive histological arrangement, which in many parts of the brain at any rate, is only to be observed in the early developmental stages, has a simple phylogenetic explanation.
Histological Study of the Degradation of Wheat Starch by Amylase.
The histological structure of the nerves is also less advanced than in the rest of the vertebrates.
Afterwards there are slight histologicaldifferentiations in its ectoderm, though the entoderm remains a single stratum of cells.
The effect, then, of this earliest histological differentiation was to produce two different kinds of cells--nutritive cells in the depression and locomotive cells on the surface outside.
Huber, at that time Assistant Professor of Anatomy, was made Director of the Histological Laboratory, becoming Junior Professor in 1899 and Professor of Histology and Embryology four years later.
The terminal portion has the samehistological characters as in the case of the hinder segmental organs.
The histologicalexamination of these bodies shewed generally the same features as in the case of the Sturgeon and Pike.
We have, moreover, made a complete series of transverse sections through one of the brains, and our sections, though utterly valueless from a histological point of view, have thrown some light on the topographical anatomy of the brain.
In our own country Mr Romaines has conducted some interesting physiological experiments on these forms; and Professor Schaefer has made some important histological investigations upon them.
Careful histological investigations, especially those of the last-named authors, have made us acquainted with the forms of some very primitive types of nervous system.
It has already been stated that in the adult we have recognized a small body which we believe to be the pancreas, but that we were unable to study its histological characters.
Teleostei; but its preservation was too bad forhistological examination.
The external opening is placed on the ventral side of the base of the feet, in the same situation as that of the posterior nephridia, but the histological characters of the vesicle are similar to those of the fourth and fifth pairs.
We have examined the histological structure of the disc at various ages of its growth, and may refer the reader to Plate 34, figs.
My study of histological sections of ventral epidermis indicates that the male does not possess a brood patch; the increased vascularization typical of the brood patch in females is not evident in males.
But it is open to question whether these effects are not exclusively due to the lesions of the blood, which are here all-predominant; for no histological modification is observed in the cells of the central nervous system.
Another histological peculiarity, not quite so universal, is the striation of the muscular fibres throughout the body.
Observations on the minute structure of the antennæ were made by many workers, but for want of good histological methods and accurate information concerning the organs of smell in other animals, these proved for a long time indecisive.
This distal thinner portion is at first without any evidence of rays; further than that there is a manifest tendency to a radial disposition of the histological elements of the fin.
The literature on the histological structure of known phosphorescent organs of fishes is rather meager and unsatisfactory.
The semicircular canals, the ampullae, the utriculus, and the cristae acusticae of the canals are normal in their general form and relations to one another as well as in their histological conditions (2 p.
Probably there are histological differences between the ear of the dancer and that of the gray mouse, which, although undetectable by scientific means at present, furnish the structural basis for the marked differences in behavior.
The material for his histological work he obtained from three different animal dealers.
Baer clearly discriminated between the type, the degree of organisation, and the histological structure.
Under these circumstances, as was shown in an excellent memoir by Kammerer,[80] they will change the whole histological type of their gills and skin in order to meet the new functional conditions.
On the other side, congenital histological adaptedness may be regarded hypothetically as due to an inheritance of adaptive characters which had been acquired by the organism’s activity, exerted during a great number of generations.
Ontogenetical growth generally sets in, both in animals and in plants, after the chief lines of organisation are laid out; it is only the formation of the definite histological structures which usually runs parallel to it.
The elementary organs are typical with regard to their position and with regard to their histological properties.
There are seen on a yellowish ground a number of small white granulations like grains of wheat, which a histological examination shows to be formed by an accumulation of embryonic cells in the spaces which separate the hepatic acini.
In many cases which have been described as primary atrophy the histological investigation of the stomach has been very defective.
Footnote 71: The histological changes here described are based upon the examination of typical specimens both of recent and of old gastric ulcers which have come under my observation.
Fraenkel of Berlin[3] is likewise due the credit of an accurate comprehension and elucidation of the clinical and histological pathology of this disease.
The chronic tuberculous sore throat of advanced tuberculosis is likewise a different affection clinically, though of the same histological character.
In the later stages, however, the gelatinous change of all the histological elements may occasion embarrassment, as at this stage the peculiarities of the cellular structure will have been destroyed.
The histological character of every cell in a multicellular organism is determined by a single determinant (cell-determinants).
Histological examination in a question of this kind might prove conclusive by showing the structure of the fibrocellular tissue that constitutes the cicatrix.
This view is strengthened by certain anatomical and histological resemblances to the genus Sternaspis, which in one species, S.
Marinesco has published another criticism of my theory in an article[9] entitled “Histological Investigations into the Mechanism of Senility.
The usual histological relation of vessels and surrounding tissues is such that both are simultaneously affected.
With an agreement as to its histological characteristics, its possible place of origin is any of the connective tissues of the body, and their presence is universal.
The color and texture, the physical, chemical, and histological characteristics, are identical.
These anatomical discoveries resulted in uniting more closely the affections scrofula and tuberculosis from the histological standpoint, and the union has become more firmly cemented from the etiological investigations.
Indeed, the structural peculiarities of the growth may be more characteristically shown in the former in those instances where the primitive tumor has undergone degenerative changes obscuring its histological features.
Avoiding the minute histological details for which the prescribed length of this article gives no scope, but little is to be added to what has already been said in the section on the clinical features of the disease.
The identification of tuberculosis with the pearly distemper and certain scrofulous affections is thus established from the etiological as well as the histological point of view.
The histological features of the tubercle were further investigated by Wagner,[47] who described the resemblances and differences of the structure of the tubercle and the lymphatic gland.
I have now to state the effect upon this hypothesis which in my opinion has been produced by the histological proof that the plexus in question is composed of fully differentiated nerves.
Now we know from histological observation that there is a plexus of nerve-fibres pervading the whole expanse of the contractile sheet, and therefore we may conclude that this is the tissue through which the effects are produced.
This is, no doubt, as I have already observed, a very remarkable fact; but it becomes still more so when we have regard to the histological researches of Professor Schaefer on the structural character of this nerve-plexus.
In evolution we should expect these to appear before the camera-like structure of a highly developed eye, while in the process of degeneration we should expect these fine histological characters to go first.
In contrast with the histological idea of a system of organs, we have the physiological conception of an apparatus of organs.
However, this histological and organological division of the two great groups of tissue-plants must not be pressed; there are many exceptions and intermediate forms.
Naturally, this lack of a visible histological structure in the plasma-globule of the monera does not exclude the possession of an invisible molecular structure.
The fact is that purely morphological observations are but preliminary steps to the histological and physiological study of the brain, and of the body as a whole.
A very accuratehistological description of these forms was given in 1876 by Richard Hertwig.
The other Thalassicollida differ from their common ancestral form, Actissa, mainly by the higher histological differentiation of the unicellular body.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "histological" in a variety of sentences. We hope that you will now be able to make sentences using this word.
