The first point to emphasize is:—Sarcoma as a central bone lesion is rare and up to the present time it is a question as to a positive five-year cure after an amputation. In Codman's registered cases of five-year cures, accepted by the committee, there are no examples of central sarcoma. The number of central sarcomas recorded in my contribution in the Journal of Radiology for March 1920, has been reduced by further study, and the two cases recorded there as five-year cures were not accepted by the committee. One of these (Figs. 23, 24, page 218, Journal of Radiology, March, 1920) I withdrew myself on further study, with the revised diagnosis of a latent bone cyst in the lower end of the femur. A second, still living more than ten years after amputation, was a typical gross example of the so-called bone aneurysm, an intact bone shell, a cavity filled with blood, with here and there more or less tumor tissue attached to the bone shell. In this case the sections did not contain the predominating and typical giant-cells of the foreign body or epulis type. Ewing and Codman viewed this registered case of mine as a variant of the giant-cell tumors, others agreed with me in the diagnosis of sarcoma. In Codman's series, and in my own, this case, Heine (Pathological Number 14229, Figs. 20, 21, in the Journal of Radiology, March 1920), is unique. In that paper I also recorded another bone aneurysm in the lower end of the femur (Figs. 11, 12) as a possible sarcoma. The Committee was about divided on the diagnosis and we now practically agree that it should be called a benign giant-cell tumor. This short statement gives but a bird's eye view of the years during which this giant-cell tumor has been recorded and treated as a sarcoma, and has given surgeons encouragement to sacrifice a limb in order to save a life, and today there are surgeons and pathologists who seem unable or unwilling to look upon this giant-cell tumor as a benign pathological process.

I early found in my studies that, among the patients living five years after amputation, there were a few central lesions diagnosed chondrosarcomas. On restudy of the tissue the histological picture was that of a chondroma. I have found in many clinics that these chondromas which present cellular areas are still called sarcomas. This group with the giant-cell tumors compose a large number of the cases registered with Codman as five-year cures after amputation.

In my list there is still one apparent bone aneurysm which must be looked upon as malignant. It was situated in the lower epiphysis of the tibia; the bone shell was intact; when first operated upon and curetted the bone cavity contained blood and a little tumor tissue, friable and hemorrhagic, resembling giant-cell tumor, but in the sections there were no giant-cells but a tumor tissue called then small round-celled sarcoma. This tumor recurred and the patient died a few months after amputation from metastasis to the lungs.

Sarcomas which have evidently arisen in pre-existing chondromas or myxomas are the only proven types of central sarcoma in which the bone shell is intact. In my cases none has survived five years after operation.

The pure myxomas may arise as central lesions just as chondromas. When these myxomas have involved bones other than the phalanges, metatarsal or metacarpal, they have been explored, removed piece-meal, recurred, then the patients have submitted to amputation and finally died of metastasis.

My second point is the natural conclusion from the statement of the first point: Central sarcoma with intact bone shell is rare, and so far, with the possible exception of my one case, there have been no five-year cures, therefore when the x-ray shows a positive central lesion there is no danger of delay.

There is no objection to trying radiation first, unless the age and the involvement of the shaft indicate a bone cyst. In this lesion diet is more important than radiation.

Our greatest responsibility is: not to make diagnosis of malignancy in benign bone cysts or advise the unnecessary expense of x-ray treatment; next, not to allow a benign giant-cell tumor of the epiphysis to proceed to the thinning and destruction of the bone shell because in this event curetting although it may accomplish a cure with bone transplantation, will not preserve the same good function.

Our next ambitious endeavor should be to recognize the possible and fortunately infrequent central chondrosarcoma or myxosarcoma, or the pure myxoma, so that we may explore under the protection of the cautery, recognize from the gross or frozen section, and radically remove by resection or amputation.

In some instances it may be possible to diagnose without exploratory incision and so resect or amputate this malignant group. Then again we must learn to pick out the benign chondromas and not submit these cases to mutilating operations. The chief danger of exploring chondroma is the transplantation of bits of tumor cartilage into the soft parts. These bits of tissue grow to new tumors.

I have sufficient evidence to indicate that something can be done for the comfort of patients with metastatic bone tumors and the temporary restoration of function by properly selected cases of resection and bone transplantation.

For the multiple myeloma, I have no data which offer any hope.

The so-called Brodie's abscess in the epiphysis or shaft, without the characteristic clinical picture of osteomyelitis and without an x-ray shadow with indication of periosteal bone formation, is very infrequent. These cases will resist x-ray and when explored the pus or granulation tissue in the bone cavity will distinguish it from other central lesions.

There is one other x-ray picture that should be mentioned here, but it will require a second paper to fully discuss it. Diffuse sarcoma of the osteoporosis or destructive type may have so little periosteal tissue and so little periosteal bone formation, that one can palpate nothing abnormal and can see in the x-ray only the localized zone of somewhat honeycombed or diffuse absorption. In all of my experience I have only four such x-rays, as this type of sarcoma is rarely cured, if ever, by amputation and often reacts favorably if only temporarily to radiation. There is no objection to the rule already given, to try x-ray first. This x-ray is usually associated with Ewing's type of tumor (a round-celled sarcoma or angio-endothelioma.)