Employing the electron microscope, the writer studied the ultra-structure of the choroid plexus of the lateral and the 4th ventricles of the brain in seven species of animals comparatively. No such extensive comparative investigation has been made before with this instrument. The animals represent, in the main, species which have served previously, both in physiological and light microscopical studies on this organ, and consist of several specimens each of the frog, the opossum, the hamster, the guinea pig, the rat, the rabbit and the dog.

Materials and methods. A technique of sacrificing the animal under deep anesthesia by decapitation was the method of choice in most cases. It permitted the exposure of the choroid plexus and the subjection of its tissues to the fixative within a period of 3-4 minutes from the death of the animal. Fixation was accomplished with 1% hypotonic osmic acid buffered to a pH of 7.3-7.4 with veronal acetate. Dehydration was performed with absolute ethyl alcohol; in some cases acetone was used as the final bath. Embedding was done in prepolymerized n-butyl methacrylate, the catalyst being 1% benzyl peroxide. Trimmed and mounted specimens were sectioned with a Porter-Blum microtome set to cut 0.05 [illegible], and suitable sections were mounted on 200 mesh copper grids. Sections so mounted were supported, in most cases, by only an amorphous film of carbon evaporated onto their surface, and were then studied with a modernized RCA EMU-2A electron microscope.

Observations and Discussion. A comparison of the choroid plexuses from the lateral and 4th ventricles did not reveal any differences in their ultra-structure and have, therefore, not been described separately here.

The writer’s description of choroidal ultra-structure is given under two main division: the epithelium and the stroma. Of these, the epithelium was found to be more complex in construction. Its free surface is characterized by a border of protoplasmic projections. These projections, usually provided with expanded club-like terminal ends, are essentially uniform in their morphology in all of the species examined except the frog where, besides the usual form, broad spatulate kinds exist. Cilia protrude from the free surface and, though seen in all the animals, are never abundant save in the frog in which they are numerous. The plasma membrane, especially the highly complex and infolded basal portion was noted constantly in every animal. The endoplasmic reticulum is composed chiefly of round or oval profiles, but small areas of the granular lamellated type are also present, these being more abundant in the frog. The Golgi apparatus consists of smooth membranes, is of typical form and is in reality a part, though a specialized one, of the endoplasmic reticulum as investigations by other authors have indicated.

The nuclei of the cells of the choroidal epithelium are large and usually round. Generally, they are located in the basal region of the cell, and do not exhibit any characteristic differences between species. Two kinds of inclusion bodies are described: one kind, eosinophil bodies in the frog, and the other kind, large frothy bodies of lipid-like materials in the guinea pig. The eosinophil bodies proved to be identical in structure with the eosinophil granules of the blood and bone marrow eosinophil cells, and mark the first instance of such a granule being reported in a location other than in those cells.

The elements of stroma, comprising blood vessels, pial cells, collagen fibrils, cement substance and basement membranes, were found to be so similar in all animal that they are discussed without reference to species. In the portrayal of the endothelial cells, attention was given to the perforation of these cells, to their relations to the supporting pial elements, and to the further relationship of pial cells to the ependyma. In the description of the basement membranes and their relation to ependymal, endothelium, pial elements and cementing substances, it is noted that cementing substances and the lamina rara interna and externa of the basement membranes are identical in appearance and are directly continuous with each other in many places.

Conclusion. In conclusion, it can be said that in regard to basic architecture of the choroidal elements, no fundamental differences seem to exist between the species of animals studied. The differences that are most marked concern certain cytoplasmic details in the frog. They are: 1) a difference in the morphology and content of some of the apical protoplasmic projections constituting the polypoid border, 2) the presence of more cilia, which also has a greater diameter than in the other animals, 3) the greater abundance of the granular lamellated types of endoplasmic reticulum membranes and 4) the occurrence of apparently typical eosinophil granules.

Certain points of evidence both for and against the secretory activity of the choroid plexus were noted secondarily.

LLU Discipline





Graduate Studies

First Advisor

Otto F. Kampmeier

Second Advisor

E. Harold Shryock

Third Advisor

Raymond A. Mortensen

Fourth Advisor

Carrol S. Small

Fifth Advisor

Guy M. Hunt

Degree Name

Doctor of Philosophy (PhD)

Degree Level


Year Degree Awarded


Date (Title Page)




Library of Congress/MESH Subject Headings

Choroid plexus; Choroid plexus--Anatomy and histology

Subject - Local

Loma Linda University. Anatomy program -- dissertations.



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Loma Linda University Libraries

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This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.


Loma Linda University Electronic Theses and Dissertations

Collection Website



Loma Linda University. Del E. Webb Memorial Library. University Archives