The Roster of Confederate Soldiers, 1861-1865, shows:

Lassiter, H.C. TN 4th Inf. Co.F
Lassiter, H.L. TN 42nd Inf. Co.A
Lassiter, Hansel L. FL 1st Inf. Old Co.E, New Co.B
Lassiter, Henry TN 21st (Wilson's) Cav. Co.I 1st Lt.

But as you can see, none of them are listed as a surgeon.

The Hansel Lassiter from Florida does look interesting though.

1st FL Inf Reg organized & mustered into Confederate service for 12 months at Chattahoochee on 4/5/61 - failed at reorganization Feb 1862 - men who enlisted organized into 4 Co's as the 1st [McDonell's] Inf Bn Feb 1862 - unit did fight at Santa Rosa Island 10/9/61

1st FL [McDonell's] Inf Bn merged with Confederate Guards [LA] Response Bn 5/1/62 as FL & Confederate Guards Response Bn - the two Bn's separated 7/17/62 - this Bn merged into 1st FL Inf Regt [reorganized] 8/15/62

1st FL [reorganized] Inf Reg organized by consolidation of 1st FL [McDonell's] Inf Bn & 3rd FL [Miller's] Inf Bn - field consolidation with 3rd FL Inf Reg from Dec 1862 to Apr 9, 1865 - consolidated with 1st FL Cav Reg & 3rd, 4th, 6th, & 7th FL Inf Regs on 4/9/65 at Smithfield, NC and designated 1st FL Inf Reg Consolidated