The first part of the book deals with anatomic investigations of the atlanto-occipital space in its relation to the puncture of the cisterna magna. It is found that the depth of the cisterna at the foramen magnum is 0.5 cm. in large dogs and 0.3 cm. in small dogs. The average amount of cerebrospinal fluid obtained was 5 cc. The white cell count increased with repetition of punctures. The second part of the book deals with the effects of an iodized oil containing 0.54 Gm. of iodine per cubic centimeter. It is a radiopaque medium which is easily tolerated by the dog and which may be used to show the location of a spinal block. It was observed that after injection in the cisterna magna it took about 110 minutes for it to descend into the subarachnoid culdesac.